LITTLETON, Colo. (AP) -- More than three weeks after the bloodbath at Columbine High, there are still some fundamental questions that investigators cannot answer with certainty, among them: Was there a third shooter?
Some students "are very adamant about the fact that there was a third gunman," said sheriff's spokesman Steve Davis. "All along we've been trying to prove or disprove that theory."Investigators are leaving open the possibility that another gunman joined Dylan Klebold and Eric Harris, but so far there has been no physical evidence to support the theory.
Some witnesses claimed to have seen a third gunman in a white shirt. But Davis said that one of the two teenagers was wearing a white shirt that day and apparently took off his black trench coat during the rampage.
Ballistic tests being conducted by the Colorado Bureau of Investigation may help prove or disprove the third gunman theory.
"We match the bullets taken from the wounded and the dead and match them to weapons taken from the crime scene," said bureau director Carl Whiteside. The tests may determine which gunman fired which shots and whether guns that are unaccounted for were used.
Whiteside said agents are testing hundreds of pieces of evidence, including bullets, bullet fragments and shell casings, and it could be weeks before the findings are in.
The findings may also help determine definitively whether the teens killed themselves or if it was a murder-suicide. Davis said the coroner's office believes both died of self-inflicted gunshot wounds.
Davis said police are busy chasing down some 2,200 leads and conducting a tremendous number of interviews.
"From the outside, it looks like not much is happening. There's not big news coming out every day," he said. "But I can assure you there is a team of about 80 investigators on this task force that are very busy."