Houston cardiologist, one-time doctor of George H.W. Bush, killed by man with 20-year grudge, police say originally appeared on abcnews.go.com

Houston police believe that the suspect who allegedly killed the one-time doctor of former President George H.W. Bush held a 20-year grudge against the cardiologist because his mother died while being operated on by the doctor.

Authorities have filed an arrest warrant for Joseph James Pappas, 62, who is believed to be armed and dangerous as well as suicidal, said Houston Police Chief Art Acevedo during a press conference Wednesday. The arrest warrant carries a charge of murder, Acevedo said.

PHOTO: Houston Police Chief Art Acevedo holds up a photo of Joseph James Pappas, the suspect wanted in the July 20 murder of local cardiologist Mark Hausknecht. (KTRK) More

Mark Hausknecht, 65, was shot on July 20 as he rode his bicycle in broad daylight in a residential neighborhood in Houston.

PHOTO: These photos released by Houston police show Dr. Mark Hausknecht, 65, riding his bike Friday before he was shot and killed. (Houston Police Department ) More

Officers searched Pappas' home early Wednesday morning and received a tip from an individual who had information about the killing, Acevedo said.

"We believe this absolutely is the killer of Dr. Hausknecht," Acevedo said.

Acevedo praised members of the community for coming forward after the latest footage was released on Monday with a clearer image of the suspect.

"Good job," he said. "Thank you for all your work. You did your part."

(MORE: New surveillance video, images released in slaying of President George H.W. Bush's former doctor)

(MORE: Police release suspect sketch in fatal shooting of President George HW Bush's cardiologist)

That footage was obtained from home surveillance, and the police department received several tips from people who recognized the man.

PHOTO: Former President George H.W. Bush waves as he leaves Methodist Hospital with his cardiologist, Mark Hausknecht, after a news conference in Houston. (David J. Phillip/AP, FILE) More

One of the callers indicated that the suspect's mother was once a patient of Hausknecht's.

Those close to Pappas have not heard from him in about 36 to 48 hours, Acevedo said, adding that the suspect allegedly sent a text to someone indicating "that he was going to kill himself."

Acevedo asked anyone aware of Pappas' whereabouts to call 911. The police chief described Pappas as a "very fit white male" and said it's "highly likely that he left his residence on a bicycle," a 10-speed Schwinn model.

(MORE: Police release suspect sketch in fatal shooting of President George HW Bush's cardiologist)

(MORE: Kansas City lawyer shot and killed in front of his home after dropping kids at school)

After Hausknecht was killed, police announced that he likely "targeted," when he was shot by the gunman, who was also on a bicycle when he rode past Hausknecht before turning and firing two shots at him.

Hausknecht was heading to work when he was shot, the president and CEO of Houston Methodist Hospital, Marc L. Boom, wrote on the hospital's website.

"He was a brilliant physician, and he's touched a lot of lives," Acevedo said on Wednesday.

A sketch of the suspect was released a day after Hausknecht was killed. The man was wearing a dark jacket when he fled the scene.

Houston police released a composite sketch of the suspect in the fatal shooting of prominent Dr. Mark Hausknecht on Friday, July 20, 2018. (Houston Police Department) More

Story continues