Detectives now believe that the Bronx honors student gunned down in a park last week may have been hit by a stray bullet after running into a gazebo to escape a thunderstorm, police said yesterday.

Kemar Bryan Brooks, 14, was discovered dead by his father early Friday after the teen was shot in the back of his head in a Baychester park, cops said.

NYPD spokesman Paul Browne yesterday said Brooks, an avid tennis player, may have gone into a gazebo near the courts for shelter during the storm Thursday night.

A witness had told cops that Brooks and another tennis player in his 20s or 30s, as well as a third man, appeared to run into the structure to avoid the rain. The witness also said she had seen a shooter enter the west side of Haffen Park and fire toward the pool, which is in the same direction as the gazebo, Browne said.