An 11-year-old Bowie girl was killed and six persons were injured, three of them seriously, in two unrelated accidents in Prince George's County early yesterday morning, according to state police.

Coleen Lawson of 12102 Tanglewood La. was dead on arrival at Prince George's General Hospital. She had been sitting in a Ford Pinto parked on the right shoulder of the outer loop of the Beltway near I-95 when the car was struck from the rear by a late model Plymouth Duster driven by Cheryl Roxanne White, 34, of Beltsville, police said.

Coleen Lawson's mother, Lida, 44, who was driving the Pinto, was reported in fair condition at Prince George's General with multiple fractures and lacerations. Jacqueline Lawson, 7, was reported in critical condition at Children's Hospital in Washington. A fourth passenger, 17-year-old Jerry Lawson, was treated and released from Prince George's General hospital.

White was treated and released from Holy Cross Hospital.

Police did not know why the Pinto was stopped on the shoulder at 6:25 a.m. or why the Duster left the road.

Earlier in the morning, a Clinton man suffered "massive internal injuries" after he ran a stop sign at the intersection of Maryland Rte. 301 and Mitchellville Road near Bowie, police said.

Anthony Morisi, 23, was flown to Prince George's General Hospital by helicopter after his 1976 Pinto struck a motor home that was traveling south on Rte. 301, according to police. The motor home fell on the Pinto, trapping Morisi for some time, according to state police. Reynold D'Amato, the driver of the motor home, was not seriously injured, police said.