SAN ANTONIO -- A Frio County Sheriff's prisoner was shot and killed Monday afternoon by a deputy transporting him to San Antonio.

Andres Gutierrez, 19, was unrestrained in the front seat of Deputy Roger Salinas' vehicle when he told San Antonio police Gutierrez began attacking him as they drove on Interstate 35 South near Fischer Road.

Salinas told police he began to lose consciousness when he fired at Gutierrez, striking and killing him, police said.

Gutierrez was unrestrained and riding in the front seat of the Frio County Sheriff's vehicle, said SAPD Sgt. Gabe Trevino.

Gutierrez died at the scene, while Salinas was taken to University Hospital with multiple facial injuries.

San Antonio police are investigating the shooting because it happened within the city limits.