Accounts such as these:
Katelyn Place: She saw a tall gunman descend the steps of the cafeteria door. He had a black trench coat and a rifle. “Kate said, ‘It was [redacted]. I’m almost positive of it. I remember looking him dead in the eye. He was in my debate class for a little bit either the end of last semester or the beginning of this one. [...] Dylan kind of looks like Robert, but Dylan doesn’t have the long face. Robert’s teeth are messed up and he was smiling and I saw his teeth then.’ [...S]he has since seen pictures of Dylan Klebold and Eric Harris, and she said, ‘It’s not one of them.’ [...]. Kate said that she looked at [redacted] for about 30 seconds until he looked at her and smiled. She remembers him shooting Ann[e] Marie. [...] Robert was randomly shooting. [...] Robert was still shooting. Kate saw Ann[e] Marie drop. Kate said that Robert shot Ann[e] Marie before he smiled at Kate. Kate looked and saw Jason [Autenrieth] trying to help Ann[e] Marie, dragging her away from Robert [...]” (pg. 4,081, Columbine Report and 7,833-8, El Paso Report).
Cara Sander: She heard about 15 shots in a matter of seconds and saw two males by the top of the outside stairs. The first subject had short dark hair, bushy eyebrows, brown eyes, and “a very full face.” He was tall and overweight, wearing a long, black, buttoned-up trench coat and shooting a large gun. “Cara said without any doubt, she is 100 percent certain the person that she saw and described as Subject #1 was [redacted]” (pp. 1,121-34). In the El Paso Report, a copy of Brian Sargent’s yearbook page is included with her interview (pg. 4,296, El Paso Report).
Ashley Egeland: She heard shots coming from the area of the library. Soon after, Egeland saw Harris and another male she recognized walk around the corner of the library into the north hall. When they noticed her they started shooting. The second male had dark brown hair (“below the ears and curled at the back”), reading glasses, a white shirt, black trench coat, dark pants, and black boots. He was about 5’8”, with a “scrawny body.” “She said that Morris was armed with a hand gun while Harris was armed with a shotgun” (5,247-58, Columbine Report).
To be honest, the stranger it gets, it's probably not true.