John Warnock Hinckley Jr., charged in the attempted assassination of President Reagan, had been under psychiatric care and was arrested last October in Nashville carrying three handguns in his suitcase during a visit by then-President Carter.

His arrest in downtown Washington yesterday apparently followed several years of aimless drifting -- years during which the 25-year-old son of a weathly western oilman dropped in and out of college in Texas and traveled through Colorado and Los Angeles in search of a job.

Law enforcement officials said that Hinckley had been in Washington only one day before the assassination attempt, staying at the Park Central Hotel at 18th and G streets NW. He told an official last night that he had received medication for five months while under the care of a private psychiatrist in Colorado.

Snapshot pictures of Hinckley over the years show the dissolution of a young man from a healthy, clean-cut kid in suburban Dallas to a disheveled, glassy-eyed drifter looking for odd jobs near his parents' new home just outside the wealthy Denver suburb of Evergreen.

Lawyer James Robinson, a spokesman for the Hinckley family, said in Colorado that Hinckley had been under psychiatric care, but he refused to provide any other details last night.

Although the parents acknowledged their son's mental problems, news that he had been arrested for attempting to kill the president came as a shock.

"This is a joke, isn't it," said Hickley's mother, Joanne, when a reporter informed her that her son was arrested in the shooting. She had been watching television reports of the assassination attempt and was not aware that her son was in Washington, she said. Then her voice began to crack, and she hung up the telephone.

"The family is grieving and heart broken by this tragedy. They love their son and will stick by him," Robinson said.

At a hearing that began just before midnight last night, U.S. Magistrate Arthur L. Burnett ordered Hinckley held without bond and directed that he undergo a mental examination today. Hinckley is being held in FBI custody at an undisclosed location.

Charles F.C. Ruff, the U.S. attorney for the District, told the court that Hinckley had been living in motels in the Denver area for most of the last two weeks and then, while telling his parents he was going to California, traveled by bus for three days from Utah to Washington.

"He has no fixed address here -- he seems to have no fixed address anywhere, Ruff said. He added that the only job prosecutors could find the suspect ever held was at a newspaper in Colorado for one week.

Hinckley, dressed in blue overalls and speaking in a soft, low voice, said he had no property or bank accounts. Burnett found Hinckley indigent and appointed two attorneys to represent him.

This was not Hinckley's first arrest, nor his first experience with hundguns.

Last Oct. 9, Hinckley was arrested at the Nashville airport while trying to go through metal detectors with three handguns concealed in a suitcase. He was released on bond and prosecutors did not press charges.

At the time, during the heat of the presidential campaign, Carter was in Nashville, arriving at the airport two hours before Hinckley's arrest. Reagan was scheduled to be in Memphis that day, but his appearance was canceled.

When arrested, Hinckley was trying to board a plane to New York, Carter was scheduled to appear there Oct. 13 and again Oct. 16. Reagan was also to be there Oct. 16.

Nashville authorities confiscated the three guns -- two cheap .22-caliber German-made revolves and a .38-caliber revolver plus 50 rounds of ammunition -- but not inform the Secret Service.

Secret Service spokesman Jack Warner said last night that federal guidelines call for written reports of such incidents to be filed with the Secret Service.

Warner said that Hinckley was not on the list of persons considered to be either potential or serious threats to the president. Warner said there are about 400 people considered "serious threats" to the president and the names of another 25,000 on file as possible threats.

"A person with three guns in a bag, not declaring them in an airport and getting on a plane the same day the president was coming through should have been reported to us," said Jack Warner, spokesman for the Secret Service.

On Oct. 13, Hinckley was in Dallas, according to law enforcement sources, and purchased two more .22-caliber handguns of the same make for about $45 apiece at Rocky's Pawn Shop. At the time Hinckley brought these guns, he gave an address of 2404 Tenth St. in Lubbock, Tex. He had attended Texas Tech in that city.

One week later, on Oct. 20, Hinckley was in Denver, applying for a job on the Rocky Mountain News. His first choice was a writing job and second was circulation, according to sources there. He said his hobbies were "reading sports and politics."

At the time he listed as previous employment the Taylor Publishing Co., in Dallas between June and August 1978, and Ellis photography in Los Angeles between June and September 1976. That information could not be confirmed last night.

On Jan. 21, of this year, Hinckley applied for an identification card from the Colorado Department of Motor Vehicles in Lakewood. He also bought another pistol in January, Ruff said at last night's hearing.

Then, on March 11, he went to GI Joe Pawn Shop in Denver and pawned an electric guitar and a manual typewriter for $100. At that time, he gave a false address. An employe of the pawnshop, who refused to give his name, described Hinckley as "very strange. He seemed spaced out -- this guy was weird."

Hinckley gave the pawn shop a home address in Dallas. He was in fact living at the Golden Hours Motel in Denver. He had checked in on March 8 and stayed there 16 days, checking out on March 23.

Unchong Lee, a clerk at the motel, said he followed the television reports yesterday and "recognized his picture right off" as being the man who checked out only last week.

"He paid a week's rent in advance -- $74.50 in cash," Lee said. "He came into the office every morning to buy a newspaper but he didn't talk very much. He was a quiet guy."

Stacey Aucort, who lived next door to hinckley at the motel, said she talked to him daily about "everyday things" but that he said nothing about his family or where he came from. "He seemed like an ordinary guy; he never talked about politics or the president," she said.

When he left on March 23, Hinckley drove off in a white Plymouth Volare, Lee said, adding, "He didn't say where he was going."

After yesterday's shooting, Hinckley was rushed to D.C. police headquarters downtown, arriving there with his hands cuffed behind his back and was rushed to the third-floor homicide squad room.

"He looked dazed, like he didn't know what was happening to him," said one policeman who witnessed Hinckley's arrival at headquarters. "When he came out, he looked really scared, like he knew" the extent of the trouble he was in.

He stayed in the homicide squad room for about an hour, sequestered in an interview room under the guard of an FBI agent and a homicide detective, while senior law enforcement officials decided who would have jurisdiction. Eventually, Ruff handed the case to the FBI.

While Hinckley was waiting in the interview room he said nothing -- except to ask for a lawyer -- and was asked nothing, according to police. "He looked at ease, just like any other prisoner; there were no emotions," said Sgt. Danny Keller. He and other policemen described Hinckley as about 5-8, 160 pounds with sandy-blonde hair, ruddy complexion and dressed in slacks and a blue-and-white shirt.

On his way out of police headquarters, Hinckley was booked and formaly charged. He was asked to answer a few routine questions about his identity. Police said he said very little.

At 5:19 p.m., almost three hours after the shootings, Hinckley was driven away in a 10-car motorcade led by two D.C. police officers on motorcycles. He was in the back of a blue Ford sedan flanked by two FBI agents. With sirens blaring and traffic stopped, the motorcade rushed off toward the FBI Washington field office at Buzzard Point.

He was questioned there in the presence of two court-appointed attorneys until the court hearing late last night. Theodore M. Gardner, special agent in charge of the FBI office, said that a physician also was present because Hinckley had complained of a sore throat. Gardner said that law enforcement officials had recovered a .22-caliber handgun at the scene of the shooting.

Hinckley is the second son of Denver oil executive John W. Hinckley Sr.

The oldest son, Scott B. Hinckley, 30, is director of operations for Vanderbilt Energy Co., the Denver-based firm founded and headed by his father. Scott Hinckley graduated from Vanderbilt University, the namesake for the family oil buisiness. Hinckley also has a sister, Diane Sims of Dallas.

Hinckley grew up in the exclusive Highland Park section of Dallas in a world replete with a country club and $200,000 homes, a quiet, wealthy neighborhood where maids answer front doors and where most houses are equipped with sophisticated and elaborate security systems.

He was 8 years old when President John F. Kennedy was assassinated in downtown Dallas.

Neighbors who remember the Hinckley's when they lived in a large two-story blond brick house on Beverly Street, near the Highland Park Country Club, recall them simply as a nice family to whom they occasionally waved.

School officials remember Hinckley as a "nice suburban kid" who attended Armstrong Elementary School and McCullough Middle School, before attending Highland Park High School. He was president of his home room in the seventh and ninth grades, played basketball in the seventh grade and was manager of his ninth grade football team.

"He was an average student, neither the type to be in the National Merit Scholarship program, nor at the bottom of his class," said Thomas Blackwell, a graduate student at the University of Texas in Dallas who said he was in the same homeroom as Hinckley. "He was not an outstanding type."

Highland Park, which was and remains virtually all-white, is "the type of school where they say prayers every day and where you occasionally see a Rolls-Royce or two around," Blackwell said.

There, Hinkcley was active in the school's Rodeo and Spanish clubs, and was a member of a now defunct organization called Students in Government.

Those who knew him then described him as clean-cut, red-cheeked youngster who was athletic and bright, but who excelled in neither sports nor studies.

"I remember him as a very personable, very polite person," said Bill Lierman of Richardson, Tex., who sponsored the school's Rodeo Club the year Hincley graduated, 1973.

It was then that the wandering, the aimless drifting began. He has spent the last eight years of his life in a spiritual, if not physical, transit. He enrolled in 1974 at Texas Tech University in Lubbock, where he remained on the student rolls until last summer.

In Lubbock, he lived in dormitories on and off campus and originally enrolled in the school's business administration college. By the end of his sometime full-time, sometime part-time academic odyssey, he was majoring in English. In between, Hinckley registered for a modern German literature course, in which the professor required students to read three elective works.

Hinckley, according to records, chose to read "Mein Kampf," by Adolf Hitler, and a study of the Auschwitz concentration camps.

Hinckley's grade point average was in the "C" ranger, according to English department records. Hinckley failed to appear for a second summer semester last year.With that, his academic record would probably have remained forgotten. But yesterday the FBI removed Hinckley's records from the university.

While Hinckley was drifting through Texas Tech. his family had moved to a rambling wood-and-stove house near Evergreen, Colo., Denver's wealthiest suburb. The move, according to family friend Robert Prewitt, a Denver oil executive, was in part brought on by the father's love for the outdoors. An avid cross-country skier, he relocated the headquarters of Vanderbilt Energy Company from Dallas to Denver in 1974.

The father, a registered Republican who contributed money to John Connally's ill-fated presidential campaign, is the chairman of the board of a corporation that explores and develops oil and natural gas reserves, and produces and sells crude oil and gas in the United States and Canada.

According to Security and Exchange Commission records, net income for the business topped $500,000 in 1979, and net revenues were $3.3 million.

"Hinckley Sr.," said John Massey, spokesman for the Oil Investment Institute, "has a good reputation. He's just a typical independent producer."

In Evergreen, a luxurious bedroom suburb where houses sell for over $250,000, few people remember the accused assailant. But yesterday there was an outpouring of shock and sympathy for the father, who was described glowingly as an affable neighbor, a respected businessman and active member of local oil and natural gas groups. Neighbors said he and his wife are active churchgoers who occasionally go to Bible study classes.

"Please, please leave us alone," a young woman at the local library stammered as she broke into tears during a reporter's interview.

"I'm absolutely sick," said Jefferson County Commissioner Jim Martin, who represents Evergreen.

Prewitt said he and Hinckley "sometimes lunch together at the Petroleum Club downtown . . . We often talked of gas and oil and politics, and I do know Jack was a firm supporter of Reagan."

Realtor Mary Lee added, "The Hinckleys are lovely, substantial people . . . This is Reagan country."

The elder Hinckley immediately left his Denver office for his home upon learning of his son's arrest.

The block on which the Hinckley's live was cordoned off yesterday by local police, and the Hinckleys, who were interviewed yesterday by the FBI, retired to the nearby home of family friends.

Hinckley said Hinckley Jr. was in Evergreen two weeks ago, when he said he was en route to California. At 5:30 p.m. yesterday, however, Hinckley was charged in Washington with assult with intent to kill a police officer, and attempted assassination of the president.

The wandering was over.