A driver’s marijuana and prescription sedative use led to the head-on crash that killed 13 people on a church bus last year, the National Transportation Safety Board determined Tuesday.

Toxicology tests showed Jack Dillon Young had marijuana and clonazepam, a sedative used to treat seizure and panic disorders, in his system. Young also said he took twice the prescribed dosage before the March 29, 2017, crash, according to a summary of the NTSB report.

Young’s truck crossed into oncoming traffic on U.S. Highway 83 near Concan, about 80 miles west of San Antonio, and slammed into the bus carrying members of First Baptist New Braunfels.

Fourteen people were on the bus,  and the driver and 12 passengers died. The victims ranged in age from 61 to 87. They had been heading back from a choir retreat.

Unsmoked and partially smoked marijuana cigarettes, drug paraphernalia and prescription and over-the-counter medication were found in Young’s truck.

A witness recorded a 14-minute long video that showed the truck crossing over the solid white shoulder line 37 times, going over the double-yellow centerline 19 times, and at one point driving completely on the wrong side of the road, a preliminary report stated.

The video ends just before the truck enters the curve where the crash occurred.

After the crash, Young reportedly told a witness he had been texting.

A summary of the NTSB report stated it was possible Young had been using his cellphone, but “this action would not explain the prolonged and continuous erratic driving behavior seen in the witness video recording leading up to the crash.”

The NTSB report also recommended lap and shoulder belts instead of just lap seatbelts be used on medium-size buses. The lap belts the passengers in the back of the bus were wearing contributed to the severity of their injuries, the report said.

Young, who was 20 at the time, has pleaded no contest to intoxication assault and 13 counts of intoxication manslaughter. He faces up to 270 years in prison at his sentencing, which is scheduled for November.

Original article posted at Dallas News. The Associated Press contributed to this report.