DALLAS (CBSDFW.COM/AP) — A motorist’s use of marijuana and a sedative led to a collision with a church bus in Texas that killed 13 people on the bus, the National Transportation Safety Board said in a report released Tuesday.

According to the report, toxicology tests on Jack Dillon Young, who survived the March 2017 crash, found the drugs in his blood stream. Young told NTSB officials that he had taken twice the prescribed dosage of the sedative before the wreck.

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church bus crash (credit: CBS)

The crash happened on U.S. 83 near the Concan community, about 80 miles west of San Antonio. The minibus from First Baptist Church of New Braunfels was returning from a senior retreat when the crash happened.

According to the NTSB findings, Dillon was driving his truck erratically on the two-lane highway for more than 15 minutes, even driving on the wrong side of the road for extended periods, and ultimately ending with in the head-on crash. Dillon also may have been glancing at or doing something on his cellphone at the time of the crash, but that wouldn’t have caused such prolonged erratic driving, the NTSB found.

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Bus lap-and-shoulder seatbelts might have averted some fatalities, the report noted. Only lap belts were provided for passengers at the rear of the bus, which the NTSB said was insufficient.

In May, Young pleaded no contest to intoxication assault and 13 counts of intoxication manslaughter. Each manslaughter carries a punishment of up to 20 years in prison, and up to 10 years for the assault charge — meaning Young could be sentenced to up to 270 years in prison. His sentencing is set for next month.

The NTSB report recommended that law enforcement officers undergo advanced training to better spot drug-impaired drivers and provide better additional tools, such as roadside drug-screening devices.

But it also said “the state of Texas needs increased safety-focused leadership at the governor and state legislature level, additional resources, and data-driven strategies to prevent tragedies such as the Concan crash and to reduce the number of fatalities and serious injuries caused by alcohol- and other drug-impaired drivers.”

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)