The Police Department Internal Affairs Bureau is investigating how a police security video that captured a young man's suicide ended up on a Web site devoted to violence and pornography, a department spokesman said yesterday. The young man, Paris Lane, 22, of Harlem, used a 9-millimeter handgun to kill himself on March 16 in a lobby at the Morris Houses project in the Bronx, where he had been visiting his girlfriend. His foster mother said yesterday that she had notified the police when she learned the video had been posted on the site. The 45-second video, which is no longer...