VAN NUYS MAN KILLS NEIGHBOR, SELF IN SPREE.

Byline: Anne Burke and Jaxon Van Derbeken Daily News Staff Writers

A man burst into a neighbor's apartment and opened fire on sleeping family members, killing one, before turning the gun on himself, authorities said Tuesday.

Hector Quintero, 29, who had been sleeping on the living-room floor in the family's studio apartment on Sylvan Street, screamed, ``Please, no,'' before Gilbert Medina, 46, fired a fatal shotgun blast at him at 11:13 p.m. Monday, said Quintero's brother, Juan, 22.

After killing Hector Quintero, Gilbert Medina, 46, fired a shot to his head, police said. He died at Holy Cross Hospital in Mission Hills.

Quintero family members said Medina was a complete stranger, and they had no idea why he broke into their apartment. Police confirmed that there was no apparent reason that Medina chose Quintero to kill.

``As far as we have been able to determine, apparently the guy just lost it somehow,'' said Lt. Richard Blankenship of the Van Nuys Division.

Juan Quintero survived the attack by hiding behind a curtain partition in the living room, he said. His wife, Patricia Corona, and the woman's 8-month-old son, Juan, cowered inside the closet.

``He was shooting all over the place,'' said a teary-eyed Quintero, seated beside Corona on a couch at the apartment of his sister, Barbara, 27, who lives in the same building. ``I thought he was going to kill us all.''

Medina broke into the locked apartment by firing a shotgun at the doorknob, family members said.

Police said Medina had called his sister to tell her he planned to kill a neighbor who had laughed at him for not being able to make rent, then kill himself.

Tenants said that Medina appeared to go berserk shortly before the attack.

About 45 minutes earlier, Medina threw plastic chairs in the courtyard of the apartment building, said building manager Elida Gonzalez.

Though he recently had fallen $150 behind on his $530-a-month rent, Gonzalez said, Medina paid all but $50 of the debt Monday, she added.

Medina had been in another deadly confrontation last year. He was arrested after a Nov. 9 confrontation with a man who later died. Charges were dropped after prosecutors ruled the incident mutual combat, Blankenship said.