A Prince George's Country man wanted in the mass slaying of his wife, two daughters and three other persons in his Camp Springs home was being sought yesterday in Chicago, where he fled after allegedly taking two hostages from the Washington area.

Ronald Ellis, the suspect in the Washington area's worst mass slaying since 1973, allegedly drove to Fairfax County after Saturday's shootings and abducted a female acquaintance and her 5-year-old son. Ellis allegedly held the hostages at gunpoint and drove to Chicago, where the woman, Mary P. Turner, and her son, Joey, escaped yesterday morning.

Ellis, 34, was named as a first-degree murder suspect in the shooting deaths of his 33-year-old wife, Ingrid, a sergent on the D.C. police force, and two of their daughters, Tammy, 12, and Monica, 4.

He also was sought in the slayings of the three others, two of whom have been identified as Sherry V. Robinson, 32, of 11300 Cheryl Dr., Upper Marlboro, and Tyrone Jackson, 12, of 4020 Clark St., Boulevard Heights. Tyrone Jackson is the son of Janet Jackson, a longtime friend of Mrs. Ellis. Identification of the sixth victim, a woman, was held up by the severity of her shotgun wounds.

The bodies of the six victims were found in the Ellis home at 6700 Coolridge Rd., a corner residence in the quiet, middle-class neighborhood. Five of the victims were in a small bedroom where they had been killed by shotgun blasts in what one law-enforcement official described as the "bloodiest murder I have ever seen." Mrs. Ellis, who was killed with a handgun, was found dead by the front door. A shotgun also was found lying inside the door.

Neighbors said the Ellises had another daughter, Tracy, a ninth grader at Walker Mill Junior High School, who police said was staying with friends at the time of the slayings.

The six slayings were the worst mass killing in the area since the 1973 deaths of seven Hanafi Muslims in a Northwest Washington house. Three years later, five members of the family of former State Department official William Bradford Bishop Jr. were beaten to death in their Bethesda home. Bishop, who was charged in those slayings, has been sought by police ever since.

Police said they believe the Ellis slayings were set off by a domestic quarrel. Some neighbors said Ronald and Ingrid Ellis, a quiet and somewhat reclusive couple, were having marital difficulties and planning to separate.

"Yes, there were problems there. And Tracy was quite open about them," said one neighbor, who added that Tracy had said she, her mother and her sisters would soon be moving out of their Coolridge Road home to live without their father.

The slayings, according to police, occurred sometime between 3 and 4 p.m. Saturday, shortly after a real estate agent showed the Ellises' five-bedroom, orange-brick split level to prospective buyers.

When the agent returned to the home at 6 p.m., she found Mrs. Ellis' body at the foot of the stairs just inside the front door. The agent ran to a neighbor's home, and police arrived to find five more victims, all dead of shotgun wounds and sprawled one on top of another in a back bedroom.

By then, according to a law enforcement officials, Ellis, apparently a gun collector who kept rifles, shotguns and handguns in a case in his den, had fled in his Volkswagen.

According to Fairfax County authorities, Ellis appeared at the home of Mary P. Turner at 3808 Laramie Pl., in the county, where he found Turner and her son.

Ellis, who knew Turner, a Safeway cashier in Crystal City almost immediately produced a gun, tied up Turner's son, and ordered the woman to follow him and the boy outside, police said. Ellis allegedly put the boy in his car and told Turner to follow him in her car.After abandoning his Volkswagen in a parking lot near Turner's home, Ellis and the boy got into Turner's car. With Ellis at the wheel, the three drove off.

About 2 a.m. yesterday, while Prince George's police were searching for Ellis, a male friend of Turner's reported her and her son missing.The friend, Theartrice (Butch) Boyd, also knew Ellis, who had done mechanical work on Boyd's car.

At about 8:30 a.m. yesterday, police said, Boyd received a phone call from Ellis, who said that he was in Massachusetts with his captives and that both would be released unharmed if police left him alone.

But Ellis and his hostages were not in Massachusetts, police later learned. They were probably somewhere in Indiana, heading toward Chicago.

About two hours later, Ellis pulled into a service area on Interstate 90 in Chicago, a few miles past the Indiana border, and got out of the car, leaving the keys in the ignition, according to Indiana state police.

While Ellis was outside, Turner started the car and sped away, driving with her son back into Indiana, where she made a frantic phone call to police.

She described Ellis as "very dangerous" and told police he was wanted in the Washington area for murder, according to Indiana state police Sgt. George Schmidt. She also told police Ellis had a "great deal" of money.

Turner was taken to a hospital with her son and then was released to return home, according to police. Police said they found two handguns believed to be Ellis' in her automobile.

The service area where Ellis got out of the car was just inside the Chicago city limits, and police said it would be quite simple for Ellis to walk off the highway and disappear into the heavily populated area. Authorities in Indiana and Illinois were searching for him yesterday.

Fairfax County Police yesterday issued warrants for Ellis' arrest in the abductions and for carrying a firearm during the commission of a felony.

Back in the Ellises' Camp Springs neighbor, where the $100,000 homes sit on expansive, well-manicured lots, neighbors were saddened by the slayings, but most said they hardly knew Ingrid and Ron Ellis, who one neighbor said "kept pretty much to themselves."

Neighbors said they had heard no shots Saturday, but added that was not surprising because the homes are so solidly constructed that noise does not travel.

When Ron and Ingrid Ellis moved to Camp Springs from Landover in the fall of 1978, they became one of the first black families in the middle-class neighborhood, buying their house for something over $80,000.

It had everything they wanted -- a bedroom for each of the three girls, room in the back for a swimming pool and a two-space garage where Ron Ellis could indulge his hobby and part-time occupation of repairing automobiles. The first couple to look at the house, the Ellises decided on the spot to buy it and had papers drafted that same day.

Once moved in, neighbors recall, the family was somewhat reclusive but otherwise a near-perfect picture of suburban domesticity. Ron, a lanky man standing over 6 feet, worked for McArdle Printers in Silver Spring at night and during the days fixed cars for private customers.

"He was a good mechanic and a nice fellow, I'll say that," recalls one of his automotive customers.

Ingrid, who joined the D.C. police force in 1970, at first commuted into the District to police jobs with the Training Academy. Recently she was promoted to sergeant, her name topping the promotion list. She was transferred to patrol duty at the 2nd District headquarters on Idaho Avenue in Northwest. She was happy with her new job, she told a former supervisor.

But at some point, serious marital difficulties had developed between Ingrid and her husband. And neighbors said Ron and his eldest daughter, Tracy, had trouble getting along. About a year ago Tracy ran to a neighbor's home seeking refuge and frantically screaming that her father was going to beat her, according to the neighbor. A second neighbor investigated, finding that Ellis was going to punish her with a switch because she had cut classes, and the daughter was returned home. Last fall, Ellis told his real estate agent that they were thinking of selling the house. He and Ingrid were having marital and financial problems, he told the agent, without elaboratinbg. Months of indecision ensued, with Ellis telling the agent he felt there was still a chance to patch things up with his wife. The house was put up for sale, then was withdrawn abruptly after a few days.

In the meantime, Ellis had fallen behind on the $765-a-month payments on the house and his bank was foreclosing. He and his wife "just weren't pulling together," he told the agent, creating the impression that he felt Ingrid was withholding some of her salary payments.

Throughout the sale process, the two behaved civilly toward each other, the agent said, discussing their future calmly and never raising their voices in front of him. It remained unclear where Ron would go once the house was sold, though the two had discussed setting him up with a repair garage of his own.

Meanwhile, Ingrid and Janet Jackson, a childhood friend, apparently were discussing setting up a joint household once the sale was concluded. As late as Friday of last week Jackson told acquaintances of this plan. Jackson's 12-year-old son, Tyrone, was one of the slain childern positively identified by police.

On April 9, the house went up for sale again. It attracted heavy interest among buyers, an agent said. Prospective buyers touring the house found that Ron had moved into a cluttered bedroom on the ground level; the girls and his wife were living on the upper floor.

An agent who called at the house on Friday to install a keybox outside so that the house could be shown if no one was home found Ron morose. He was "having some problems," he told the agent, who inquired about getting a car fixed, and would be in touch once they were ironed out.

On Saturday aftermoon at about 2:30 p.m., realty agent J. Flood took a party of four to inspect the house. Wearing blue jeans and white sneakers, Ron Ellis politely answered the door, took the agent's card and excused himself to return to a kitchen chair where he was taking a phone call.

The buyers roamed through the house, finding the girls' rooms clean and full of toys, but parts of the downstairs in disarray. They caught snippets of Ron's phone coversation: "Let me talk to Mom now," and "Hi, Gorgeous," he said, causing the agent to assume he was talking either to his mother or to his wife and children.

Eillis stayed on the phone throughout the inspection, then showed the party to the door about 2:45 p.m. Later that afternoon, the party that had looked at the house called the agent to say they wanted to make a formal offer of $99,000. Agent Flood called the Ellis home and got no answer, then drove to it.

The door was bolted. Flood took they key from the agent's box and unlocked the door. She recalled: "I opened it a tiny bit and yelled, 'Is anybody home?" And I opened it a little more and I saw a body on the floor and I shut the door." Then she ran to call the police.