Three black teens aged 13-19 charged with murdering 64-year-old white homeless Roger Borkum. Attack caught on surveillance showing suspects sneaking up, kicking, and stomping victim viciously. Teens left him in pool of blood with trail down sidewalk. They rummaged his backpack post-assault then returned 20 minutes later for more kicks. One teen claimed Borkum ''dissed'' his ''dead homies'' sparking confrontation. Nearby robbery also linked to group. Victim was ex-World Trade Center worker fired months before 9/11. Witness identified assailants leading to arrests. Marcavion Lacey admitted seeing white dude ''laying'' and falling during interaction. Teens claimed not trying to kill him. Sheriff notes young offenders' devastating impact.