HOUSTON, July 20 (Xinhua) -- Spokesman of former U.S. President George H.W. Bush said Friday afternoon that the former president was deeply saddened by doctor Mark Hausknecht's death and sent condolences to his family, colleagues and friends.

"Mark was a fantastic cardiologist and a good man," Bush said. "I will always be grateful for his exceptional, compassionate care. His family is in our prayers."

In 2000, Hausknecht appeared at a news conference with George H.W. Bush after the former president was treated for an irregular heartbeat.

According to the Houston Police Department, the doctor was shot dead Friday morning while riding a bicycle in Houston, U.S. south state of Texas.

The gunman, also on a bicycle, rode off after the shooting and is on the run, Houston police said. It's not known if the shooting is thought to be random or targeted.