Image copyright CBS Image caption Dr Hausknecht famously treated former US president George Bush Snr

The suspected killer of a former surgeon for ex-President George H W Bush has killed himself as officers closed in on him, say police.

Joseph James Pappas, 62, allegedly killed cardiologist Mark Hausknecht last month over a 20-year grudge.

In 1997, Pappas' mother died on the operating table as Dr Hausknecht was treating her.

Pappas - who police say had compiled an intelligence file on the victim - worked as a policeman for 30 years.

Top doctor killed in '20-year-old grudge'

Surveillance video captured the attack in broad daylight on 20 July, showing a cyclist riding behind the 65-year-old cardiologist.

He overtakes him, then stops and turns back, before shooting him twice near a noisy construction site.

Image copyright Houston Police handout Image caption Joseph James Pappas had "a very extensive intelligence file" on Dr Hausknecht

Houston Police Chief Art Acevedo told reporters on Friday that Pappas was wearing a bulletproof vest and appeared to take a tactical position behind his vehicle's engine block after a first officer arrived on the scene.

After a second patrol car arrived from a different direction, Pappas shot himself once in the head, said Chief Acevedo.

He added that he was "thankful" the suspect had committed suicide.

"You normally don't put on a bulletproof vest when you're thinking about suicide," he said.

"I'm convinced that if we had not had that second officer arrive from a different angle, we would have had a shootout here."

During a search of Pappas' home, officers discovered "a very extensive intelligence file" on Dr Hausknecht.

"He knew everything you could possibly find on this man," the chief said.

When asked about Pappas' motive, Chief Acevedo told reporters "the only connection" police could find thus far "is the fact that Dr Hausknecht operated on [Pappas'] mother over 20 years ago and she died on the operating table".

"Look, the human mind is very fragile," he said. "If you try to use logic to an illogical act, which is murdering somebody in cold blood, you're already down the wrong rabbit trail."

Meanwhile, a family friend of Pappas in northern Ohio has come forward to say that he deeded her his Houston home one day before the doctor was killed.

Jeanette Spencer - who has known Pappas for 25 years - said that when she called him, he explained that he was giving her the home because he had a "terminal illness".

Ms Spencer's adult daughter - who Ms Spencer said Pappas had previously "taken under his wing" when she lived in Houston years ago - was meant to meet up with him on 30 July during a visit to the city.

Instead, he texted her that day to say that he was going to kill himself and gave her "detailed instructions to secure the house".

"Sorry for handling things this way," the text, obtained by The News-Herald, said.

"House and property is now yours. Please make best use of it for you and [your daughter]."

The daughter alerted police, who went to the home but found no trace of Pappas.