EL DORADO, Ark. (AP) — The driver of a private security van ferrying prison inmates through southern Arkansas fell asleep behind the wheel, causing a crash that killed two prisoners and injured four others, authorities said.

Gregory O. Reed, 43, of Texas, was driving a van for U.S. Extradition Service Inc. when he dozed off early Friday, the Arkansas State Police said.

Cpl. Jeff Hust told the El Dorado News-Times that prisoners began screaming, "Boss! Boss!" and that another guard grabbed the wheel but overcorrected. The van struck a culvert and went airborne, rolling twice before stopping.

Shawn Talbot, 29, of Ladysmith, Wis., and Walter Ridley, 47, of Clarendon died at the scene.

Seven inmates and two guards were in the van, which was on its way to Little Rock. Both guards were wearing seat belts, while the inmates were unsecured in the back of the van.