A terminally ill doctor carrying “numerous” guns held an Austin medical office hostage for hours on Tuesday before fatally shooting a local physician and himself, police said, shaking the Texas capital city and leaving investigators hunting for a possible motive.

Following a standoff that lasted more than six hours, officers entered the Children’s Medical Group building in central Austin on Tuesday night and found the suspect, Bharat Narumanchi, a 43-year-old pediatrician from southern California, dead of an apparent self-inflicted gunshot wound, according to police.

Nearby, officers said they found Katherine Dodson, also 43 and a pediatrician. She, too, had been fatally shot, police said.

It’s not clear what prompted Narumanchi to target the office, but investigators said his failing health may have been a factor. According to police, he had recently been diagnosed with cancer and was given just weeks to live.

“We feel like his terminal cancer probably played a large part in whatever occurred in his life,” Jeff Greenwalt, a police spokesman, told reporters Wednesday.

Why he targeted Dodson was an even murkier question, according to police. Though she and Narumanchi worked in the same field, they may not have known each other. At some point last week, Narumanchi had visited the office and applied for a volunteer position, police said, but aside from that encounter, “there did not appear to be any relation or other contact between Dr. Dodson and Dr. Narumanchi.”

The apparent murder-suicide touched off a wave of mourning for Dodson, a mother of three who won honors and accolades for her pediatric work.

“Last night, in a horrifying act of gun violence, one of our most skilled, compassionate pediatricians, Dr. Lindley Dodson, was held hostage and murdered at her Central Austin office,” Rep. Lloyd Doggett, a Democrat who represents part of the Austin area, wrote on Twitter. “She provided care for our youngest 2 grandchildren & so many other children across the community.”

“At 43, her life has been cut terribly short,” Doggett added. “She leaves behind her husband Drew and three children. What a tragic, tragic loss.”

The hostage incident began about 4:30 p.m. Tuesday, when Austin police responded to a call reporting a disturbance at the Children’s Medical Group building in the Oakmont Heights neighborhood.

Shortly after arriving, officers learned someone was barricaded inside the building and requested a SWAT team. For hours, members of the SWAT team pleaded with the suspect to answer their calls or text messages.

“You can come out of the front door with your hands up and empty and follow the instructions of the officer,” the negotiator with a megaphone yelled, in video captured by reporters on the scene. “I know you’ve been dealt a very terrible card, but you’ve spent your entire life dedicated to other people.”

After several hours of silence, police sent a robot unit inside.

According to police, members of the SWAT team decided to enter the building after losing contact with the suspect for several hours.

About 10:50 p.m., loud bangs erupted from inside the building. Moments later, images from the robot revealed at least one person was dead inside, police said Tuesday. When SWAT members stormed the building in a rescue attempt, they discovered the other body.

Greenwalt, the police spokesman, told reporters Wednesday that Narumanchi had “numerous guns on him” but didn’t offer specifics on the types of firearms. In a statement, police said Narumanchi was armed with a pistol and what appeared to be a shotgun, and was carrying two duffel bags.

According to Greenwalt, Narumanchi took several hostages once he entered the building, ordering some of them to “tie themselves up.” Over the course of the standoff, he said, Narumanchi let some go and others managed to escape.

Investigators are now looking for friends and associates of Narumanchi who may be able to shed light on what motivated him.

Police have already made contact with his family, who were cooperating with the investigation, Greenwalt said. It was not clear when he was diagnosed with cancer, according to Greenwalt, but the family was “entertaining hospice care.”

“The case — as far as who did this — is closed,” Greenwalt said. “But we really, really want to answer the question of why and provide as many facts and circumstances to the family and friends as we can, and provide as much closure in this tragic situation as we can.”