SLIPPERY ROCK TWP — No criminal charges will be filed against a Slippery Rock University student who was driving a sport utility vehicle that slammed into the side of a tractor-trailer here in September, killing one of her passengers.

Instead, state police this week cited Hollie Carlson, 20, of Markleton, Somerset County, for a pair of traffic violations, including running a stop sign.

Investigators believe Carlson caused the deadly collision Sept. 10 when she did not stop at the intersection of Route 8 and Branchton Road.

Her friend and fellow SRU student, 21-year-old John Tyler Stufflebeam of Warren, Pa., was killed in the early-morning crash.

The nearly four-month investigation determined Carlson was not criminally liable for Stufflebeam’s death, authorities said.

Trooper Robert Rottman Jr., the investigating officer, on Wednesday issued her traffic citations for careless driving and the stop sign violation.

The careless driving ticket carries a $500 fine and the failing to stop at a stop sign ticket carries a $25 fine.

She has 10 days from the time she receives the citations to plead guilty and pay the fines and court costs, or plead not guilty and seek a summary trial before District Judge Tim Shaffer.

Carlson could not be reached for comment Wednesday.

Police and Butler County District Attorney Richard Goldinger did not immediately return telephone messages.

Police said Carlson was traveling west on Branchton Road about 2:35 a.m. and drove into the intersection, hitting the side of the semitractor with a flat-bed trailer that was traveling north on Route 8.

Carlson was driving Stufflebeam’s 2011 Ford Escape, and Stufflebeam was riding in the right rear seat. Four other passengers also were in the SUV but were not injured.

Rottman noted in the careless driving citation that there were six people in the “five occupant vehicle.”

The collision spun the SUV clockwise, causing its back end to hit the trailer and throwing Stufflebeam out the back window. None of the passengers were wearing a seat belt, police said.

Carlson was treated at Grove City Medical Center for minor injuries and released.

Michael Minium, 44, of Clarion, the driver of the rig, was not hurt.

County Deputy Coroner Dennis Trzeciak pronounced Stufflebeam dead at the scene. An autopsy found he died of severe head injuries.

He was a senior at SRU and was vice president of the Green and White Society for student ambassadors. Also, he was active in volunteer programs that help children with autism and spina bifida.

Stufflebeam was a 2008 graduate of Warren High School.

Among his survivors were his mother and father, and two brothers, ages 8 and 10.