There was no known connection to the school, Browne said.
None of the 38 boys studying at the school witnessed the shooting because they were at a church rehearsing, school receptionist Allie Roma said.
"We didn't hear the gunshots, but we saw the flashing lights," Roma said.
Roma said to her it appeared the man had been shot in the face.
"The body was on the sidewalk," Roma said by telephone before she was interrupted by someone who told her to hang up, which she did.
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Associated Press writer Jim Fitzgerald contributed to this report.