Houston Police released a photo of Joseph James Pappas, 65, who is a suspect in the murder of Dr. Mark Hausknecht
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Houston Police Department
Houston Police released new video of the man who they believe shot and killed prominent cardiologist Dr. Mark Hausknecht in broad daylight on June 20. In the video, taken from a residential surveillance system, the suspect is seen riding a bicycle through a nearby neighborhood "immediately following the doctor's shooting," according to Houston PD. The footage is from the same Houston street where neighbors were going door to door asking others to scrub through surveillance footage looking for images of the suspect.
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Former President George Bush, center, waves as he leaves with cardiologist Mark Hausknecht, left, and Bush's family doctor Ben Orman, right, after a news conference at Methodist Hospital Friday, Feb. 25, 2000 in Houston. Bush spent Thursday night in a Florida hospital and was released Friday after being treated for atrial fibrillation. He returned to Houston Friday and was admitted to Methodist Hospital for further tests. (AP Photo/David J. Phillip)
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Former President George Bush, center, waves as he leaves with cardiologist Mark Hausknecht, left, and Bush's family doctor Ben Orman, right, after a news conference at Methodist Hospital Friday, Feb. 25, 2000 in Houston. Bush spent Thursday night in a Florida hospital and was released Friday after being treated for atrial fibrillation. He returned to Houston Friday and was admitted to Methodist Hospital for further tests. (AP Photo/David J. Phillip)
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(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.
Houston Police Dept
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 Wednesday, but the call went to voice mail.

That phone number 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 the shooting.

It is unclear whether any of the firearms listed online were used in the shooting. A spokesman for Houston police declined to comment on the ads.

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

Suspect worked as a constable for decades

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 Harris County as a peace officer and a reserve officer from May 1983 to July 2013.

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 last year, and appeared to own multiple guns, police said.

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.
Houston Police Department
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.
Houston Police Department/Houston Police Department
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.
Houston Police Department/Houston Police Department
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.