Separate collisions on O'ahu yesterday left two people in critical condition at The Queen's Medical Center.

A 48-year-old motorcyclist from the Salt Lake area of O'ahu was injured at about 5 p.m. when his 1997 Harley-Davidson motorcycle hit the rear of a Chevrolet pickup truck as the two vehicles were heading south on H-2 Freeway about three miles north of the Ka Uka Boulevard off-ramp.

Police investigators said the cyclist apparently was attempting to change lanes when he ran into the pickup. The motorcycle operator was not wearing a helmet, police said. He was taken to Queen's, where his condition worsened from serious to critical, police said. He remained hospitalized this morning in critical condition.

Police had few details about the second incident but said a teenage boy was critically injured last night after he crashed a motorized "razor-type" scooter on 10th Avenue in Kaimuki.

Teen arrested in robbery

A 15-year-old boy was arrested on suspicion of robbery at the Stadium Mall about 7:45 p.m. yesterday.

Police said the boy entered a mall store and left without making any attempt to pay for the items he was seen taking from store shelves.

A mall loss-prevention officer attempted to detain the boy, but the boy overpowered the officer, broke free and ran a short distance before arriving police officers stopped and arrested him.

Man, 42, arrested in sex assault

A 42-year-old Wai'anae man was arrested on suspicion of multiple sexual assault offenses yesterday after a 12-year-old girl told police an acquaintance of her family had assaulted her for the past five years.

Police obtained a search warrant and went to the man's home, where they arrested and booked him for investigation of 12 counts of first-degree sexual assault, nine counts of third-degree sexual assault and one count of promoting detrimental drugs.

Girl, 17, caught driving stolen van

A 17-year-old girl was arrested in Mililani early yesterday morning after she was caught driving a van that a 29-year-old Waialua woman had reported stolen earlier.

A patrol officer spotted the van about 1:30 a.m. and noticed it was on a list of vehicles that had been reported stolen.