The 19-year-old son of an NYPD detective was fatally shot in broad daylight yesterday near a playground at the Marcy Houses in Bedford-Stuyvesant. Sean Hayes, 19, was struck in the chest around 2:30 p.m. by the Flushing Avenue playground, where children were playing on their day off from school for the Martin Luther King Day. "When I heard the shots I ran," one 10-year-old boy told the Daily News. "That's what you're supposed to do."

The teen's distraught father, Det. Sean Lawrence, a 20-year NYPD veteran assigned to the Brooklyn warrant squad, spoke to reporters outside his Queens home last night, saying, "We're trying to hold it together. We've got a lot of family here. Everybody will take a piece of my sorrow with them to make it less for me."

Hayes lived with his mother about a block from where he was killed; a cousin tells the Post, "He loved his mother and he was close with his dad as well." At the time of the shooting, Hayes was outside talking with a friend, and investigators believe the killer might have been armed with a shotgun, explaining Hayes's nine bullet wounds. At least one man was taken into custody and released last night.

Another relative, who is also a city detective, tells the News, "We don't know what happened yet," but an NYPD source tells the Post the murder was in retaliation for a prior dispute and that Hayes was the intended target. Hayes also had "a minor criminal record," according to one source.