We may never know what made Joseph James Pappas kill himself after a highly-publicized manhunt.
Police say Pappas murdered Hausknecht on July 20 as revenge.
Retired FBI Special Agent Dennis Franks has been following the case closely.
"The way it sounds like he meticulously planned the murder," Franks said. "I would bet that he meticulously planned what was going to happen afterwards, too."
Houston police said Pappas had two guns and full body armor when a parks board member approached him on the morning of Aug. 3.
By all indications, he was preparing for a shootout but ended up killing himself when two officers got to him.
"They were more in a strategic position where he couldn't shoot at both of them at the same time," Franks explained. "Maybe that was a factor in his decision to go ahead and end his own life."
Police said Pappas made no real attempt to disguise himself.
"There's a distinct possibility that he wanted to get caught. Maybe it was a challenge to him. Maybe it was a cat and mouse game," Franks said.
- Joseph Pappas stalked Dr. Mark Hausknecht at least 5 times before killing him: sources
- Dr. Mark Hausknecht's murder captured on video by METRO bus, HPD chief says
- TIMELINE: How police closed the net around man accused of killing a Houston doctor
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