He was the clean-cut, all-American boy who excelled at sports.
David Bieber assumed the identity of Nathan Coleman in the UK
The son of a respected high school principal, David Bieber was a well-mannered, friendly student.
Yet, his life - and character - changed after he left college and began to indulge his interest in body building.
No-one would have believed the former US marine would eventually flee the United States - and murder a policeman in the UK.
But his former classmates at the Fort Myers High School in Florida are still coming to terms with the 38-year-old's conviction for the Boxing Day killing of Pc Ian Broadhurst in Leeds.
Greg Martin, a friend of Bieber's who is now a teacher, told the BBC: "We had no signs anything like that would happen.
"His father did a good job raising him and I know he is heartbroken about it.
"David was bright, polite, very athletic - really the best athlete in the school - and always well-mannered."
It was when Bieber left school that his demeanour began to change.
Despite briefly joining the Marine Corps he was discharged about a year later.
After training to use an M-16 rifle and handguns the recruit was discharged from the force for taking unauthorised absence.
At home, Bieber's sport of choice was bodybuilding and his life revolved around his local gym.
He became involved in steroids and came to the attention of the Lee County Sheriff's Department, who believed he was involved in the distribution of the drugs.
An officer who came into contact with Bieber, Sergeant Dean Taber, did not share Mr Martin's opinion of his character.
1995, February - Markus Mueller shot dead in Fort Myers
1995, November - Michelle Marsh survives attack by the same gunman
1996 - David Bieber obtains passport and leaves the US
1998 - Bieber arrives in Yorkshire
2003, Boxing Day - Pc Ian Broadhurst shot and fatally wounded
2003, December - David Bieber arrested in Gateshead
2004, January - David Bieber charged with murder and attempted murder
"My impression of him was that he thought, 'I am better than you - you're not going to catch me.' He was that type of person. He thought he was better than everybody else," he said.
Bieber was friends with a German-born fellow weightlifter called Markus Mueller who was also on the department's radar.
But their relationship turned sour when Mr Mueller formed a relationship with Bieber's wife, Danielle Labelle.
Ms Labelle told the US television programme America's Most Wanted that Bieber had threatened Mr Mueller after finding out, though she dismissed it as "a game".
Mr Mueller was shot dead outside his apartment in Fort Myers on 9 February 1995.
Police questioned Bieber in the belief he had hired a hitman to kill Mr Mueller, but were forced to release him because of a lack of evidence.
In November 1995, another one of Bieber's enemies, former girlfriend Michelle Marsh, was attacked by the same gunman - though all four shots missed.
This time Bieber fled the state, assuming the identity of Nathan Wayne Coleman through a stolen passport and escaping the country in 1996.
In the late 1990s he arrived in Yorkshire where he worked as a nightclub doorman, married - and divorced - a North Yorkshire woman and built up a cache of weapons and ammunition.
It was not until the shooting of Pc Broadhurst in December 2003 that Bieber became known to police again.
Under his assumed name Nathan Wayne Coleman, he became the subject of one of the biggest manhunts ever seen in Yorkshire.
Pc Broadhurst was shot in the head and abdomen
Assistant State Attorney Scott H Cupp confirmed the Florida authorities would be seeking to extradite Bieber after he completes his sentence in the UK.
He said: "While I don't think it would necessarily be a death penalty case that we would pursue, we would still be going for premeditated murder and conspiracy to commit murder, which are obviously very serious crimes."
Meanwhile, Greg Martin can scarcely believe the David Bieber he once walked the high school corridors with is the same man who shot a police officer in cold blood.
"It is a very sad story for everybody involved. The victims as well as the criminal in this case," he said.
"All the talk has been, 'Have you read the papers? Have you seen the news? What happened to David?'
"Some people are saying, 'Was it the steroids? Could they have affected his mind?'
"We just can't believe it, that a classmate of ours is a murderer."