The seats of the van had been covered with plastic bags, court documents state.
"He came prepared to bury that guy, if not dismember him," said a source familiar with the investigation. "This wasn't a spontaneous rage. This was preplanned."
Burton, 42, the owner of Final Impact, a car-stereo and alarm shop in Morton, is due in Springfield district court tomorrow for his preliminary hearing on first-degree murder and related charges. He's being held without bail at the George W. Hill Correctional Facility.
Investigators believe the killing was the result of a love triangle.
Stropas, 32, an Army sergeant from Norristown who had recently returned from his second tour in Iraq, had been dating Burton's estranged wife, according to police. Burton and the woman were in the midst of a divorce.
Evidence indicates that the killing - Springfield's first homicide in five years - was premeditated, but it is unclear why Burton allegedly killed Stropas last Monday at 10:50 a.m. in the parking lot of the Olde Sproul Shopping Village on Baltimore Pike.
Burton, of Newark, Del., was apprehended minutes later at nearby Smedley Park while driving Stropas' Jeep Cherokee with the body on the passenger-side floor. Two county detectives spotted the vehicle shortly after witnesses reported the stabbing. Stropas had bled out in minutes and was pronounced dead at the scene.
Search-warrant applications state that Burton had been using his laptop and a wireless Internet card to track Stropas through a GPS device planted on the underside of the Jeep Cherokee. A representative from the company that manufactures the device told an FBI computer-forensics expert that Burton had accessed it 10 minutes before Stropas was stabbed.
When stopped by police, Burton said, "He came at me with a knife. I had to protect myself," according to the criminal complaint. But stab wounds were discovered on Stropas' back, sources said. Police recovered a bloody knife with a broken handle in the Jeep.
Burton's attorney, Mark Much, did not return a phone call yesterday seeking comment. Springfield police declined to elaborate on the case.
"It's hard because he just came home," Stropas' father, Peter, said last week. "He was involved with the VA and was looking into picking up his life."
Staff writer Michelle Skowronek contributed to this report.