Four people were killed in two unrelated car accidents yesterday, including a head-on collision in which a woman died after being hit by a juvenile who was being pursued by District and Prince George's County police.

Terry Marie Walker, 35, of Suitland, died after her Mercury was hit by a Toyota that had been stolen and was being pursued by police eastbound on Suitland Parkway, authorities said. The 14-year-old driver of the stolen vehicle crossed into the westbound lane of traffic, authorities said, and crashed into Walker's car just east of Silver Hill Road about 1:30 p.m.

Walker was declared dead at the scene, and the youth, whose identity was not released, was taken by helicopter to Children's Hospital, where he was listed in critical condition early this morning.

In an unrelated accident, two brothers and a third man died after their car slammed into a tree in the 14000 block of Duley Station Road in Upper Marlboro.

Prince George's police said that Chris Netherton, 18, and his 21-year-old brother, Brent, both of the 5900 block of Croom Station Road, were killed about 1:50 p.m. when the car in which they were riding failed to negotiate a curve. A third man, 21, also was killed. His identity was withheld.