Prince George's County police said yesterday that they were satisfied that two young men from Howard and Anne Arundel counties were the only suspects in the fatal stabbing of a University of Maryland sophomore early Sunday morning.

Although they initially sought three men in the killing of Brandon J. Malstrom, Cpl. Joe Merkel, a Prince George's County police spokesman, said yesterday that investigators concluded they could not bring charges against a third man who had been questioned in the attack.

County police also explained why they concealed from the public for two days the arrest and formal charging Sunday of John Ryan Schlamp, a 24-year- old Columbia resident, with first-degree murder.

They did not release his name to the public until Tuesday, they said, because they feared it would interfere with their pursuit of a second suspect - Quan Lewayne Davis, 23, of the 7600 block of Fox Trail Court in Hanover, Anne Arundel County.

"We felt that releasing the information would compromise the investigation," said Cpl. Diane Richardson, a county police spokeswoman. "We did not do it lightly."

Davis was arrested Tuesday afternoon in the 7000 block of Troy Hill Drive in a Howard County office park, Prince George's police said, and was formally charged with first-degree murder.

Both men were being held without bond last night at the Prince George's County Detention Center in Upper Marlboro.

According to court documents, Davis and Schlamp encountered Malstrom at a party in the 7300 block of Dickinson Ave. in College Park, where they demanded that he give them his cell phone. When he refused, Schlamp punched Malstrom, who was fatally stabbed in the scuffle that followed.

Investigators said it was unclear who had stabbed Malstrom.

Why Schlamp and Davis were at the College Park party remained a mystery yesterday.

Though Davis' last known address is in Anne Arundel County, he and Schlamp were athletes with strong ties to Howard County. Davis was a point guard and running back at Oakland Mills High School in the mid-1990s and was described by a friend as a "sports fanatic" who would spend hours playing basketball and football.

Schlamp had played football for Howard High School.

Davis "was a cool person to chill with. He didn't have any problems with anyone," said Andrew Jackson, who used to play basketball with Davis at the courts near Talisman Lane in the Owen Brown area of Columbia, where Davis lived during the late 1990s, according to court and county records.

High school teammates said that Davis, who was listed at 5 feet 3 inches on a recent speeding ticket, was a leader on the basketball team, where he was a pass-first point guard.

"He was the leader, the guy we would all huddle around when things weren't going well," said Murray Graves, who used to play forward on the Oakland Mills team. "It doesn't sound like him at all to get involved in something like a stabbing."

While court documents show that Davis has had only minor brushes with the law, Schlamp's involvement with the criminal justice system includes alcohol-related and assault charges.

Twice, Howard County District Court judges have ordered him to be evaluated for alcohol and drug abuse. Once, a judge ordered him to attend a 26-week treatment program and Alcoholics Anonymous meetings - and to read and report on a book detailing alcoholism.

Both times, Schlamp received a break from the criminal justice system that allowed him to keep a clean record.

After the first break - probation before judgment for a 1997 assault on a Howard police officer - Schlamp's father, John, wrote Judge Neil Edward Axel to ask that his son be allowed unsupervised probation. Ryan Schlamp, he wrote, was working full time as a cook at a Bob Evans restaurant.

"He comes home quite dirty and smells from the work. I am pleased and proud he has continued to work despite all that," John Schlamp wrote. His son, he said, was "straightening out his life."

Last year, when he received probation before judgment for driving while intoxicated, the younger Schlamp was working at Lone Star Steakhouse in Columbia as a server, according to court documents.

Sun staff writer Laurie Willis contributed to this article.