It took seconds for renowned cardiologist Mark Hausknecht, who counted a former president among his patients, to be gunned down as he cycled to work clad in his scrubs last month in Houston. But police believe 20 years of resentment harbored by the son of one of his former patients boiled over and led to the killing.
Houston police said they have evidence that Hausknecht was targeted by a 62-year-old man named Joseph James Pappas, who is still at large.
Pappas' mother died more than two decades ago during surgery performed by Hausknecht, according to police Chief Art Acevedo.
"So it appears that this may be a 20-year-old grudge that this man held," Acevedo said. "There was a lot of planning that went into this," he said, adding that the shots fired "took some skill."
Surveillance video images taken on the morning of July 20, released by police, show Hausknecht pedaling north on Main Street on his way to work. As he crosses an intersection, the suspect, whose face is obscured by a white cap, can be seen cycling closely behind, toting a "fully loaded, olive green backpack."
One block away and moments later, Hausknecht was shot, police said.
It happened near a noisy construction site with hundreds of workers milling about, some of whom Hausknecht, 65, would regularly greet as he cycled past, CNN reports. But none heard the shots, the noise of their equipment drowning out the sound of a firearm.
In the days that followed, police appealed to the public, urging residents to comb through their home security footage for any possible images of the suspect. That plea appears to have helped crack the case.
Acevedo said home surveillance video led to a tipster recognizing and identifying Pappas on Tuesday.
As authorities try to locate Pappas, they are once again requesting help from the public. Acevedo asked anyone who spots Pappas to call 911, rather than confront him directly, because "he is considered to be armed and dangerous," adding that Pappas possesses more than one firearm.
Pappas is also believed to be suicidal, in part because he sent a text message to an unidentified person saying he was going to kill himself, Acevedo said, adding that no one had heard from the suspect in days.
Police said they searched Pappas' home. "Besides the fact of the surgery of his mom, we have plenty of evidence that ties him to this crime," Acevedo said, declining to go into specifics. "We believe that this absolutely is the killer."
The Houston Chronicle reports that Pappas served in the Harris County Constable's Office, citing records from the Texas Commission on Law Enforcement.
While Acevedo said those reports were unconfirmed, "we do have some indication that many many many years ago he might have been a constable."
Meantime, the community was mourning the prominent doctor whose life was cut short after almost four decades in practice.
Houston Methodist Hospital, where Hausknecht worked, said in a statement that "his patients appreciated his kind bedside manner and the extra time he took to answer their questions."
Among those patients was former President George H.W. Bush, who appeared next to Hausknecht during a 2000 news conference at the hospital after being treated for an irregular heartbeat.
Following Hausknecht's death, the former president released a statement expressing deep sadness.
"Mark was a fantastic cardiologist and a good man," Bush said. "I will always be grateful for his exceptional, compassionate care."
Acevedo noted that the case has been on the "front burner" for the department.
Hausknecht "was a brilliant physician and he touched a lot of lives," the police chief said.