Now, investigators say, he may have taken the keys to the case to his grave.
Andrew Thomas, 44, has only one prior arrest, for a minor theft, before the deadly shooting on Thursday evening. Police say Thomas shot Officer Bradley Fox then killed himself in Plymouth Township.
However, Thomas was no stranger to police.
"The bad pennies just keep turning up," said Superintendent William Colarulo of the Radnor Police Department. Back in 1999, Colarulo led the Philadelphia Police investigation into the disappearance, and presumed murder, of Thomas' fiancee, Maria Procopio.
Procopio vanished after leaving her job at QVC in September of that year. Police could never pin the crime on Thomas, but uncovered a lot during their investigation. For example, what they found when they entered his Center City apartment at 2400 Chestnut.
"Tables covered with phony ID cards, phony social security cards, counterfeit money, night vision equipment, books on how to scam people, ammunition," said Colarulo.
Thomas eventually went to federal prison for counterfeiting, denying any knowledge of Procopio's disappearance. He continued to deny any involvement even after video of a man, resembling Thomas, was seen using her ATM card in the days after she disappeared.
After more than 30 years as a police officer, Superintendent Colarulo said Andrew Thomas was one of the most bizarre criminals he has ever encountered, and he is not surprised by last week's explosion of violence that cost Officer Fox his life.
"The spot that he told us to dig, we found a satchel full of handguns," Colarulo said.
While Thomas was handcuffed in a holding cell notice him putting his hand to his mouth.
"He had to be restrained, and what we found was a handcuff key under his tongue," said Colarulo.
In the wake of last week's deadly confrontation in Plymouth Meeting, Colarulo is trying to resign himself to the fact that the exact fate of Maria Procopio may never be known for sure.
Andrew Thomas has taken the answer to his grave.