WASHINGTON -- After a frustrating 20-month investigation into the shooting deaths of three young employees at a Starbucks in this city's upscale Georgetown neighborhood, police arrested a Washington man yesterday who they believe acted alone and charged him with murder.

A District of Columbia superior judge issued an arrest warrant for Carl Derek Havord Cooper, 29, charging him with murder.

Yesterday, police from the district and Prince George's County, along with FBI investigators, said their collaborative efforts led to the arrest, which came despite little evidence and no known witnesses to the July 1997 slayings.

"We would love to be able to solve every homicide within two minutes after it occurs, but it just doesn't always work out that way," said District Police Chief Charles Ramsey. "This is one that did prove to be complicated, but it also demonstrates the resolve that our detectives have in trying to bring these cases to a successful conclusion. They simply never give up."

The victims -- Mary Caitrin "Caity" Mahoney, 24; Emory Allen Evans, 25; and Aaron David Goodrich, 18 -- were killed execution-style. Their bodies were found in the back room of the coffee shop at the end of the July Fourth weekend.

The shootings -- in what police suspect was a botched robbery -- shocked the Northwest Washington neighborhood and hit home in Baltimore, where Mahoney and Goodrich had spent much of their youth and many of their relatives live.

For these family members, the wait for an arrest has been agonizing.

"I was afraid it was so long that maybe it would never happen," said Fran Block of Baltimore, the mother of Goodrich, who lived in Washington. "It's hard to look at the person -- I saw [Cooper] on TV. It's hard. You think, this is the last person who ever saw my son alive."

Authorities would not comment freely on the investigation yesterday, saying it is not formally closed. But law enforcement sources said they believe that Cooper killed the three alone.

"At this point, it appears he was the lone gunman, that he was the only gunman," said Anthony Patterson, the first police detective on the scene after the shootings and a lead investigator in the case. "I'm just glad it's finally over."

Earlier yesterday, federal officials released a second suspect whom they had picked up Thursday on a federal firearms charge. That man, Keith Covington, 32, of Mount Rainier in Prince George's County, was questioned for a day in the Starbucks case but was released.

Law enforcement sources said they interrogated Covington based on information from Cooper, who had grown up near Covington and had accused him of participating in the killings. Officials suspect that Cooper knew Covington lived in the same Mount Rainier apartment building as Evans, one of the victims, and led police to him so that casual connection might look incriminating and divert suspicion from himself.

But the U.S. attorney's office issued a statement yesterday saying that after further investigation, authorities had found no probable cause to hold Covington.

"Whoever set it up, they set me up good," Covington said.

Cooper was arrested this week in the attempted murder in August 1996 of Bruce Howard, an off-duty Prince George's police officer. Cooper is being held at the Prince George's County Detention Center.

The U.S. attorney's office said it is considering seeking a penalty of life without parole in the Starbucks case because of the number of victims. Authorities also are considering charging Cooper under a federal anti-racketeering statute, which would allow them to prosecute him for robberies and other crimes in Maryland and elsewhere.

U.S. Attorney Wilma Lewis said it is "premature" to speculate whether the case would be pursued in federal court. "It's a matter that is still open" to consideration, she said.

Cooper became a suspect in the Starbucks case a few months after the killings. Detectives said they had received an anonymous tip that Cooper was the gunman but did not arrest him because they lacked evidence. For more than six months, police wiretapped Cooper's telephones, hoping he would talk about the case.

Last week, authorities said, they sent an informant to Cooper's Northeast Washington home with a tape of a tabloid television show that recently aired an episode on the case. The informant, a friend, told Cooper that the authorities were closing in on him and urged Cooper to cooperate with them, law enforcement officials said.

Initially, police suspected two shooters in the Starbucks slayings, because two types of shell casings were found at the scene. But in the attempted murder of the Prince George's officer, authorities say, the assailant carried two guns. Law enforcement sources believe that Cooper was carrying two weapons in the Starbucks shootings as well and that he fired both guns there.

Yesterday, Dean Torrenga, Starbucks' regional director of operations, thanked authorities and said of the victims, "We will never forget our partners and their tragic loss."

The Starbucks company offered a $125,000 reward for information leading to an arrest. Torrenga said the award would not be given until a conviction is attained.

Relatives of the victims thanked police last night and expressed relief.

"There's some form of closure in that a suspect has been charged," said Patrick Mahoney of Towson, the older brother of Caity Mahoney. But, he added, "obviously just because a suspect has been charged doesn't mean that the family gets Caity back."

Pub Date: 3/06/99