The suspected killer of President George H.W. Bush’s former cardiologist may have targeted the famed surgeon because his mother died on the operating table two decades ago, police said Wednesday.

A manhunt is underway for Joseph James Pappas, 65, who is suspected of shooting Mark Hausknecht, 65, on July 20, police said. Pappas is armed, dangerous and potentially suicidal, authorities said.

Houston Police Chief Art Acevedo said that authorities have an arrest warrant for Pappas, who is believed to have targeted Hausknecht for the death of the suspected shooter’s mother.

“He’s dangerous, he’s capable and if you spot him please call 911,” Acevedo said, noting earlier that Pappas appears to be suicidal based on text messages that he had sent and the police department’s investigation.

Police previously released surveillance images of the shooting, which took place as Hausknecht rode a bicycle to work, and shared eyewitness testimony of the shooting. The suspected killer was reportedly wearing a baseball hat, sunglasses, a grey warm-up jacket and khaki shorts at the time of the shooting.

Hausknecht was a cardiologist at the Houston Methodist Hospital and the Debakey Heart & Vascular Center. He was announced dead at Ben Taub Hospital, a local trauma center, shortly after he was brought there by emergency services.

This is a developing story, please check back for updates.