A man who police allege is an "enforcer" for Baltimore area drug gangs was arrested yesterday on a D.C. Superior Court warrant charging him with murder in last month's execution-style slayings of three men in a Northwest Washington town house, D.C. and Baltimore police said.

Police officials said Vernon Allen Collins, 35, was arrested without incident about 10:30 a.m. after more than 20 police officers surrounded his house near Pikesville in Baltimore County. A 357-magnum revolver, a stolen 12-gauge shotgun, "an arsenal" of ammunition and a small amount of cocaine were found in a subsequent search of the house, they said.

Collins was charged in a warrant with felony murder in the shooting deaths of brothers Robert and George Cooper and Gary Milton Stevens, whose bodies were found May 10 in Robert Cooper's town house at 60 Adams St. NW.

Police sources said about 12 shots were fired in the slayings, and that each of the men had been shot at least once in the head.

According to a D.C. police affidavit filed in support of the arrest warrant, Collins, possibly acting with others, killed the three men and robbed them of heroin and about $7,000 in cash.

The affidavit is based on an account from an unidentified witness who told police that on several occasions before the slayings, he had met with Collins and Stevens, one of the victims, and discussed plans to rob the Cooper brothers at the Adams Street address.

According to the affidavit, the three apparently intended to carry out the robbery together the day of the slayings, but the witness fled when he heard gunshots inside the house. The affidavit says the witness later was contacted by Collins, who allegedly told him that "singing birds don't live long."

D.C. police sources said that Collins will be questioned in more than 10 other drug-related killings in the District and Maryland, including a double slaying a year ago today in which Samuel M. Tucker, a local pharmacist, and another man were fatally shot in the head in Tucker's 13th Street NW office.

The D.C. police Internal Affairs Division launched an investigation into the 13th Street killings when financial records found at the scene showed that Tucker had received about $50,000 from D.C. police Officer Vernell R. Tanner, police sources said.

Tanner, whose police powers have been revoked as a result of an unrelated matter, said yesterday that the money was for a "straight-up business deal" but declined to elaborate.

Police sources said Tanner also had told investigators that he and Tucker made at least one trip to Baltimore in an attempt to recover $56,000 Collins owed Tucker.

Baltimore police said Collins had served a prison term on drug violation charges and has been an associate of Anthony Grandison and Bernard (Ghost) Kane, two of Baltimore's most notorious underworld figures.

Kane was sentenced in April to 30 years in prison in a federal drug case.

Grandison has been convicted of arranging the machine gun slayings of two persons -- one of whom was scheduled to testify against him in a federal drug case -- at a Pikesville motel in April 1983. He was sentenced to death for his role in the shootings, and two months ago the sentence was unanimously upheld by the Maryland Court of Appeals.

Collins, who was being held in the Anne Arundel County Detention Center yesterday pending a court hearing in Baltimore, also was charged in April in the District with possession of cocaine, police officials here said.

A month earlier, according to Baltimore police, he was arrested on drug and weapons charges in New Jersey after police stopped his car on a traffic violation and confiscated a quantity of heroin and a 9-mm handgun.

In addition, Baltimore police said, Collins has been charged previously -- but not convicted -- in two other homicides, two cases of assault with intent to murder and one of conspiracy to commit murder.

Robert Cooper, 43, and George Cooper, 60, two of the victims in the Adams Street killings, were the brothers of Vernon Cooper, who in a recent court case was described by prosecutors as one of Washington's "kingpin" drug traffickers. Vernon Cooper was acquitted in February 1984 of charges that he headed a massive heroin ring here but was convicted and sentenced to two years in prison on income tax evasion charges growing out of the same case.

According to the affidavit filed in Collins' case, the unidentified witness discussed three times with Collins and Stevens the idea of robbing the Cooper brothers.

On the morning of the killings, the affidavit says, the witness drove to the Adams Street address with Stevens, and Stevens told the witness he had $7,000 cash with which to buy heroin from George Cooper, saying "this was the night" they were going to rob the brothers.

On their way to the house, according to the affidavit, the witness saw Collins and two other persons in a car. Stevens and the witness then entered the house, left with George Cooper for a short time, then returned to the house and entered through the back door.

The witness, who was the last to enter, told police he ran from the scene when he heard shots ring out as Stevens and Cooper entered the house, the affidavit says.

Sources close to the investigation of last year's double killing at 1829 13th St. NW said Tucker and Samuel Williams, a native of Nigeria, were found fatally shot in separate rooms of Tucker's first-floor medical office.

The sources said six packets of cocaine, two cutting blades and traces of PCP and heroin were found in the office. A police official said that Tucker, 43, of 5921 Second Place NW and Williams, 40, of Silver Spring were wearing smocks and may have been cutting drugs when they were shot in the head.

Other police sources said records of Tucker's telephone calls indicate that he spoke to Collins about 90 minutes before he was slain.

D.C. police narcotics investigators said Tucker was an associate of the Coopers and that a 1984 gambling raid on a Cooper relative's residence turned up a receipt for $25,000 paid by Tucker to a Nigerian to travel to Amsterdam, apparently to buy heroin.

Police sources said Tucker's teen-age son had gone to the 13th Street office shortly before the shootings to have lunch with his father and saw him in the office with Williams and two other men, who immediately ran into another room.

After the shootings, the sources said, the son was shown a number of mug shots of members of a Baltimore area drug gang and picked out two men who he said resembled the men he had seen in his father's office. However, sources said, the son's identification was not considered strong enough, and the men were not arrested.

In their search of Tucker's office, police also found financial records listing a number of Swiss bank accounts and "many large checks" that Tucker had written, including one for $35,000, police sources said.

Records also showed that Tucker had a financial relationship with Tanner, 39, a 17-year veteran D.C. police officer who has told investigators that he had given Tucker $50,000 to invest in a Nigerian oil deal, sources said.

In a brief interview yesterday, Tanner said he did not give money to Tucker for investment in a Nigerian oil deal but would not elaborate, saying the information he gave to police internal affairs investigators was confidential.

"I had a straight-up business deal. It didn't work out and I lost my money. That's it," Tanner said. "I had records and documentation. I informed the FBI of some things that I had concerns about . . . and they were satisifed."

In another investigation involving Tanner, police and the FBI are looking into payments of $21,000 to Tanner from the D.C. Coalition for the Homeless for advance rent on a Northwest Washington home that Tanner intended to buy but did not then own.

That investigation is part of a larger probe into allegations that the coalition may have misspent or improperly diverted thousands of dollars of federal funds.

In April, Tanner's police powers were revoked, and he was reassigned to administrative duties pending completion of the police and FBI investigation. Sources said Tanner asked this week to be placed on administrative leave without pay, but that no action had yet been taken on the request.