A Charles County, Md., deputy sheriff was killed yesterday when a gasoline tank truck jackknifed and crushed his patrol car at the intersection of Rtes. 301 and 228 in Charles County, police reported.

A sheriff's spokesman said Dennis L. Riley, 28, of Indian Head had stopped his police car for a stoplight at the intersection when a Speedy Oil Co. tractor-trailer struck the rear of a southbound car on Rte. 301, then overturned on top of the police car.

The tanker apparently was trying ti stop for the traffic light when it struck the first car, police said.

The driver of the tank truck, Richard Booth, 40, of Oxon Hill, was listed in fair condition at Physician's Memorial Hospital in LaPlata. Police did not identify the driver of the first car struck or indicate whether that driver was injured.

Traffic was rerouted for seven hours following the 10:30 a.m. accident while gasoline was pumped out of the tanker and the truck was turned upright.Some gas spilled, police said, but there was no fire.

Police also said it took seven hours to remove Riley's body from his car.

The cause of the accident was still under investigation last night.