HOUSTON -- A driver who told police he fell asleep behind the wheel fatally hit two good Samaritans who were pushing a pickup truck that broke down on an east Houston freeway on Friday, KPRC Local 2 reported.

Houston police said a man and woman in different cars stopped to help the stranded driver and helped push the disabled pickup truck off Interstate 10 near Uvalde Road at about 8:30 p.m.

Investigators said a passing driver fell asleep and hit the three vehicles.

"The two that unfortunately were killed in the accident were just passersby that stopped to help," Officer G.W. Cormier said. "They were in the rear of the truck that was hit and they were killed instantly."

The man and woman's names have not been released.

Four others were injured in the incident and taken to hospitals for treatment.

Police said they do not believe drugs or alcohol were involved.