Police searched for suspects Saturday in the shootings of three police officers in two separate incidents, including one in which a Brooklyn officer was critically wounded, apparently with his partner's gun.

In an incident that marked the first serious police shooting in the city this year, a brazen murder suspect came out shooting from his Brooklyn apartment Friday, striking a detective in the shoulder then reaching over him to shoot his partner in the head as he raced up the stairs, police said.The officer hit in the head, William Gunn, 28, was in very critical condition at a Brooklyn hospital with extensive tissue damage to the right side of his brain, officials said.

In another shooting incident earlier Friday, an off-duty police officer was shot and wounded during a mugging in Manhattan.

A $25,000 reward was offered to anyone with information leading to the arrest and conviction in the Brooklyln shooting.

The suspected gunman in the Brooklyn shooting was identified as Ralph Richardson, 20, who is wanted on murder and gun possession warrants in Harrisburg, Pa., and in Connecticut. Police also want to question him about a Jan. 15 killing in Brooklyn, authorities said.

When three plainclothes officers, including Gunn and Det. Louis Rango, went to question Richardson about the Brooklyn killing, the suspect opened his apartment door and began firing, shooting Rango in the shoulder and Gunn in the head, police said.

After the gun battle, Richardson managed to elude an army of police who cordoned off the area and conducted a door-to-door search with bloodhounds.

In the other shooting, police officer James Laskowski, 36, was shot and wounded by two muggers who jumped him as he was walking to work at Police Headquarters in lower Manhattan. He was listed in stable condition at Bellevue Hospital.