A Worcester, Mass., man accused of threatening to kill Secretary of State George Shultz and possibly President Reagan was arrested yesterday morning with a cache of weapons in his car at a Northeast Washington motel.

Edward Lewis Gallo, 41, was charged with illegally transporting firearms across state lines.

A phone call from Gallo's mother to the Worcester police Monday night set off a chain reaction culminating in an early morning teletype message from State Department officials to District police that a heavily armed Gallo was headed here.

Gallo was apprehended by police as he was leaving his second-floor room at the Regency Congress Inn at 600 New York Ave. NE where he had checked in late Monday afternoon, police said.

They later recovered one semiautomatic rifle, two shotguns and 325 rounds of ammunition from the trunk of a black 1986 Buick Century parked outside Gallo's room. He also was carrying $7,600 in cash when arrested, police said.

Gallo struggled briefly with the two police officers who confronted him, and one officer's handgun accidentally discharged, police said. No one was injured by the bullet, but the officer dislocated his shoulder in the struggle.

As police were leading Gallo away, he said he was an American citizen and a tourist who was visiting Washington and "was going hunting."

"Ordinarily an AR-15 semiautomatic rifle and a sawed-off 12-gauge shotgun would not be the type of weapons a person would use for hunting purposes," said Capt. William White III, a police spokesman.

Police cordoned off about two miles of heavily traveled New York Avenue NE from Florida Avenue to Bladensburg Road at 7:20 a.m. and it was not reopened to traffic until about 1 p.m. About two dozen motel guests were evacuated from their rooms and kept in a room at the Envoy Motel across the street at 501 New York Ave. NE.

White said that police received a teletype message from the State Department's Boston field office at 3:37 a.m. that Gallo was on his way to Washington. The message, which described Gallo's car, said that he was believed to be "heavily armed with weapons and presented a possible threat to Secretary of State Schultz and/or President Reagan," White said.

The lookout was broadcast over police radios, and about 90 minutes later 5th District police officer George E. Sullivan spotted the car on the lot of the Regency Congress motel. After interviewing the motel clerk, Sullivan discovered that Gallo was registered at the motel.

The D.C. police Emergency Response Team immediately surrounded the motel, White said, and two officers confronted Gallo at 8:25 a.m. as he emerged from Room 208.

Gallo was carrying five shotgun shells in his jacket, receipts for an AR 15 rifle and a shotgun, and keys to the Buick, police said..

After getting a warrant to search Gallo's room and car at 12:30 p.m., police found an AR15 semiautomatic rifle, a 12-gauge pump shotgun, a 12-gauge sawed-off shotgun, nine ammunition clips and 325 rounds of ammunition in the car. All the weapons were fully loaded, White said.

Gallo, a chemist, had been living with his mother, Rose, in Worcester, according to an affidavit from the State Department's Boston field office. The Vietnam veteran has been unemployed for 14 months, but worked for 10 years beginning in 1976 as a chemical laboratory chief at the Upper Blackstone Water Pollution Abatement District sewage plant in Milbury, Mass., the affidavit said.

Gallo's colleagues at Upper Blackstone expressed surprise yesterday at his arrest, and said he never talked about Vietnam, guns or politics. "It's hard to believe," said William Wrightson, who replaced Gallo as laboratory chief. "He was technically very good at his job, very intelligent."

Arthur Levesque, a plant manager, said yesterday that Gallo was "well liked, capable, smart, an excellent employe."

Rose Gallo said her son has been emotionally unstable for two years and claimed to be hearing voices but his condition had worsened during the past two weeks, the affidavit said.

When her son watched television news programs, he became agitated if the broadcast involved Shultz or the president, Gallo said. She also told authorities that last week her son said, "Kill, kill Reagan," the affidavit said. Gallo left his house Sunday with guns wrapped in a fatigue jacket and told his mother, "Shultz, you're dead," she told officials.

After her son left, Rose Gallo called the Worcester police department and told them he was driving to Washington, police sources said. Worcester police contacted the State Department's Bureau of Diplomatic Security field office at about 5 p.m.

Staff writer Nancy Lewis contributed to this report.