A Texas man was listed in critical condition Tuesday at Parkland after his truck veered off the road and slid down the Denison Dam.

Oklahoma Highway Patrol troopers said that at approximately 2:30 p.m. a truck was seen smashing through the guardrail, rolling through the large rocks on the embankment.

“The truck was really mashed up and witnesses state that no one had come out and that the vehicle was still intact, so we called for extrication and also rope rescue,” said Denison Assistant Fire Chief Bill Ray, who arrived first on the scene.

The driver was identified as Aristides Sanchez Hernandez, 50, of Sherman. He suffered massive head injuries and was taken to Parkland in critical condition.

The victim was wearing a seatbelt at the time of the accident.

Investigators did not see any signs of the driver hitting the brakes. Authorities continue investigating the cause of the accident.