A heart doctor who treated former President George H.W. Bush was biking to work when he was gunned down by another cyclist on Friday, authorities said.

The former president released a statement about Dr. Mark Hausknecht, 65, after he was shot dead near Texas Medical Center in Houston.

“Mark was a fantastic cardiologist and a good man,” Bush said. “I will always be grateful for his exceptional, compassionate care.”

The gunman remained at large on Friday night.