POUGHKEEPSIE, N.Y. (AP) _ A teen-ager accused of killing his parents and younger brother owned a variety of military paraphernalia and told police his nickname was ''Rambo'', authorities said.

Brian Britton, 16, pleaded innocent Wednesday to three counts of second- degree murder. He also pleaded innocent to one count of second-degree attempted murder for allegedly wounding his 18-year-old sister, Sherry Britton, at their home in the nearby Town of Poughkeepsie.

He was held without bail.

Miss Britton was in stable condition late Wednesday after surgery for head and chest wounds, according to a nursing supervisor at Vassar Brothers Hospital.

Killed in the shooting spree were Dennis Britton, 44, his wife, Marlene, 42, and 8-year-old Jason Britton.

Town of Poughkeepsie police displayed two guns they believe were used in the shootings, a 20-gauge shotgun and a 12-gauge semiautomatic shotgun. The weapons were found in the attic of the Britton home, police said.

Also on display during a news conference was a range of military paraphernalia, including canteens, army fatigues, canvas ammunition packs, a copy of Soldier of Fortune magazine and a smoke grenade, which belonged to Brian Britton, police said.

The teen-ager also had Rambo posters in his room and a magazine from the ''Rambo III'' movie, about the Vietnam War veteran portrayed by Sylvester Stallone, police said.

''I'd say he had a definite fixation on Rambo and military activity and military life,'' said Town of Poughkeepsie Police Chief Stanley Still Jr.

Still said police think the shootings may have been sparked by a running argument in the household over school work.