Man critically wounded after being shot in head

A 21-year-old man is fighting for his life after being shot in the head in Flatbush overnight. 
According to police, the shooting happened at 585 East 21st St. at around 3 a.m. 
The victim, whose identity has not yet been released, was rushed to Kings County Hospital where he is listed in critical condition. 
It is not yet known what led to the shooting, and there were no witnesses. 
Anyone with information is urged to call Crime Stoppers at 1-800-577-TIPS