Montgomery County police are looking for the driver of a dark midsized car that sped away after hitting and killing a 30-year-old pedestrian who was crossing Piney Branch Road in Silver Spring late Tuesday.

Rick Janisch of 8301 Garland Ave., Takoma Park, died of head injuries at Washington Adventist Hospital about 11 p.m., shortly after he was hit by a car that was headed toward the District, police said. Police said he was crossing in the middle of the block near Dale Drive.

In an unrelated accident, three Rockville teen-agers were hospitalized, two of them in critical condition, after the driver of a car they were in lost control on a curve on Avery Road and hit a tree Tuesday night. Two other passengers were treated at Suburban and Shady Grove Adventist hospitals and released.

Geehreng said the 1987 Chevy Cavalier was exceeding the speed limit near Norbeck Road in Rockville when the car, driven by Scott Bolon, 18, crossed the center line.

Bolon, a recent graduate of Rockville High School, is in critical condition in Suburban Hospital's intensive care unit, with broken arms and legs and facial bones, according to a hospital spokeswoman.

Kelvin Oie, 16, who was in the back seat, is also in critical condition at Suburban with facial injuries. Aaron Weitzman, 18, the front-seat passenger, was in fair and stable condition at Shady Grove Adventist Hospital.