Armed with a knife and his Chevrolet Avalanche, Lawrence Maurice Crawley showed up at his ex-girlfriend's Montgomery County workplace shortly after 2 a.m. Friday, authorities said. During a break in her overnight shift, he attacked, chasing her, stabbing her, and running her over repeatedly with his 5,000-pound SUV, according to court documents.

By the time police arrived, 33-year-old Angela Maya Stith was already dead. Her body had been left in her employer's parking lot. The final minutes of her life, police said, were captured on surveillance cameras outside Vector Security, the Plymouth Meeting security system business where she worked.

"It is disturbing," a visibly emotional Montgomery County District Attorney Kevin Steele told reporters Friday afternoon. Crawley "hits her again and again. He makes passes by her and crushes her."

Crawley, 33, of Philadelphia, was arrested Friday on charges of first-degree murder and related offenses.

After the attack, authorities said, he fled the scene, going west on the Pennsylvania Turnpike. State Police spotted him driving on the turnpike in Somerset County, about 80 miles east of Pittsburgh. When they pulled Crawley over and approached his SUV, he set himself on fire, apparently in an attempt to avoid arrest, authorities said.

He was taken to a local hospital, where he was in critical but stable condition Friday afternoon, Steele said.

Stith and Crawley had an "on-again, off-again" relationship, but were not together at the time of the killing, Steele said. The two were texting, and may even have been talking on the phone before the attack.

At 2:13 a.m., security footage showed Stith walking out of a rear door of Vector Security, which is in an office park off Butler Pike. Her cell phone appeared to be illuminated as she walked toward her Toyota Solara and got inside. The attack began while she was sitting in the driver's seat, police said. She escaped from the passenger side of the vehicle and began running away from a man chasing her, they said.

Crawley soon caught up with her and began stabbing her — over and over, authorities said. Coworkers ran out to the parking lot to try to help her — to no avail. Crawley had gotten into his SUV. He drove in circles around the parking lot, running over Stith three times before fleeing, according to the documents.

This was not the first time Crawley had been violent, according to police and court records. In May, he was charged in Montour County with choking Stith, eventually pleading guilty to a lesser charge of simple assault, according to Montgomery County authorities.

In 2015, Crawley was charged in Duval County, Fla., with battery, assault with a deadly weapon, and false imprisonment. He pleaded guilty to battery and was sentenced to a year in prison, court records show. The details of that case were not immediately available Friday, and it was unclear  how much time he served.

In Montgomery County, authorities said Stith did not have a restraining order against Crawley, Steele said.

"It is our nightmare in these cases, that it escalates to this point," Steele said. "This was a terrible death."

An autopsy confirmed Stith's death as a homicide, caused by blunt- and sharp-force trauma.

It was unclear when Crawley would be arraigned on murder charges due to his condition, Steele said. There will be no bail, he said, since prosecutors have charged him with first-degree murder. No attorney for Crawley was listed in court documents Friday.

Whitemarsh Township Police said the attack was the municipality's first homicide in 17 years and stressed that there was no current threat to public safety.