Even after he was hacked in the head with a hunting knife, a Brooklyn cop still managed to chase his attacker across a subway platform - shooting him twice before collapsing nearby, police said yesterday.

NYPD Officer Angel Cruz fell to the ground within 3 feet of the wounded suspect and knelt over him until backup arrived late Tuesday and arrested the man, police said.

"When police found them, Cruz was on one knee," a police source said. "He wanted to cuff the guy but he \[Cruz\] had lost so much blood it was all he could do to stay upright."

Cruz, who joined the force about 15 months ago, was in critical but stable condition yesterday at Jamaica Hospital. Although the brutal blow cracked his skull, he was able to talk to his wife and 2-year-old son. He even joked a bit with visitors.

"The doctor says this is a lucky guy," Mayor Bloomberg said after visiting Cruz. "Unlucky in that he gets stabbed. Lucky that he is going to make a full recovery."

Hugo Hernandez - an illegal Guatemalan immigrant who sneaked back into the U.S. after being deported for attacking six cops in New Jersey - stabbed Cruz after the cop spotted him and his pal Andy Batista smoking in the subway station about 11 p.m., police said.

Cruz told them to put out the cigarettes and ordered them to come with him so he could issue them summonses, police said.

Batista, 21, complied, handing over identification and an Army knife. But Hernandez, 22, punched Cruz without warning on the Queens-bound platform of the J train, police said.

Hernandez then pulled out a 6-inch blade and slashed Cruz across the face, police said.

Blood flowing down his neck, Cruz fell backward against a pay phone as Hernandez allegedly came at him a second time with his knife raised.

Cruz fired three times but missed Hernandez, who lunged forward and jammed his hunting knife into the 30-year-old officer's left temple with such force that it pierced his skull, police said.

"A witness sees the perp stab the knife in the cop's head and pull it out," a police source said.

Cruz somehow fired two more rounds and hit Hernandez twice in the left elbow as the suspect fled down the stairs to the Manhattan-bound platform, police said.

Cruz ran after him, following him down the stairs to the other platform. "Covered in blood, a hole in his head, about to faint, he doesn't give up; he's tough," a fellow cop said.

Sgt. James McNamara heard the gunshots, yelled into the transit precinct offices inside the subway station and raced to help.

McNamara and Officers Robert Velez and Christopher Ballaera found Cruz kneeling near Hernandez and cuffed the suspect, police said.

Officers Anthony Cairone and Jumel Gungor carried Cruz out of the station, put him into a .patrol car and drove him to Jamaica Hospital.

When they arrived, Cairone threw Cruz over his shoulder and carried him inside.

Hernandez, who was in stable condition at Brookdale University Hospital, was charged with attempted murder of a police officer and criminal possession of a weapon. He also faces up to five years in prison for sneaking back into the U.S., authorities said.