CNN  — 

A man whose mother died during surgery 20 years ago is the suspect in the fatal shooting of a prominent Houston cardiologist who performed the operation, police said Wednesday.

Chief Art Acevedo said the mother of Joseph James Pappas, 62, was a patient of Dr. Mark Hausknecht, who was fatally shot as he rode his bicycle to work at Houston Methodist Hospital on July 20. Police earlier said Pappas was born in 1953.

Houston Police released a photo of Joseph James Pappas, who is a suspect in the death of Dr. Mark Hausknecht.

“So, it appears that this may be a 20-year-old grudge that this man held,” Acevedo told reporters.

CNN called a phone number listed for Pappas’ real estate company on Wednesday, but the call went to voice mail.

That phone number also is linked to recent listings on a firearms auction website for several guns, ammunition, tactical vests and ballistic plates for car doors. The posts, from a user in Houston, apparently went online days after Hausknecht was shot.

It is unclear whether any of the firearms listed online were used in the shooting.

A spokesman for Houston police would not comment on the ads.

Suspect likely owned several guns, chief says

Acevedo said a tip came in Tuesday after surveillance video released a day before showed the suspect, whom someone said they recognized. Police got a search warrant and went to Pappas’ home, but he was not there.

Acevedo said Pappas had made phone calls indicating he was considering suicide. The suspect has not been seen in almost two days.

“This man is dangerous. This man is capable. This man has some skills (with firearms),” he said.

There was evidence at the home linking Pappas to the killing, the chief said. A lot of planning went into the killing, according to Acevedo.

The suspect appeared to own multiple guns, he said.

Pappas worked for 30 years as a constable, according to Texas Commission on Law Enforcement records.

He worked for both Harris County Constable Precincts 2 and 7 as a peace officer and a reserve officer from May 1983 to July 2013.

Pappas took law enforcement classes through August 2017.

Video captured images of suspect

The renowned cardiologist, who treated former President George H.W. Bush, and the suspect were seen shortly before the shooting riding their bicycles on South Main Street, police said.

This surveillance image shows a suspect in the shooting of Dr. Mark Hausknecht, police say.

Surveillance footage showed the suspect following Hausknecht as both pedaled north, police said.

Hausknecht’s wife, Georgia Hsieh, said police told her that her husband was riding through a construction area when the gunman rode up in front of him and fired three shots while facing him.

The cardiologist was found feet away from the construction site, where about 500 workers were on duty at the time, a construction manager at the site said. But no one heard anything because of the equipment.

Hausknecht, circled in green, was followed by a cyclist, in red, shortly before the shooting, police say.

A close-up surveillance image showed the suspect wearing a blue, short-sleeve polo shirt, a khaki or white cap, khaki shorts and an olive-green backpack, police said.

The suspect, circled in red, nears Hausknecht on the road.

Other surveillance images showed the suspected gunman just behind Hausknecht as both headed north on Main across West Holcombe Boulevard, police said.

Police highlighted Hausknecht with a green circle and the suspect with a red circle on images posted on Twitter. The fatal shooting happened moments after that crossing, one block away, police said.

CNN’s Jamiel Lynch, Holly Roberts, Sonia Moghe, Majlie de Puy Kamp, Lauren Leslie and Jason Hanna contributed to this report.