Police release photos of former Bush cardiologist and suspect moments before fatal shooting

Houston police continue their search for the person who killed Mark Hausknecht.

Police have released images from the moment right before a onetime doctor for former President George H.W. Bush was gunned down as he rode his bicycle in Houston.

Cardiologist Mark Hausknecht, 65, was shot and killed as he rode his bike Friday, according to Houston Methodist Hospital. In a statement, his wife Dr. Georgia Hsieh called her husband's death "devastating."

In still photos released Sunday, police used the color green to indicate Hausknecht and red for the suspect.

"The Dr. is headed north at 6700 Main & crossing into the W Holcombe Blvd intersect," police said.

"[In the] 2nd & 3rd photos are suspect behind the Dr. The shooting happened moments later, one block away," the police said in a post on Twitter.

"This 4th (and last) photo is moments after the shooting as the suspect heads west on Southgate Blvd toward Travis St. These are the only images available for release at this time," police said.

Former president George H.W. Bush released a statement about Hausknecht's death through his spokesman.

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

Houston police also released a composite sketch of the suspect on Saturday.

Police said they are searching for a white or Hispanic male suspect about 30 years old who was wearing a dark jacket and fled the scene.

The suspect was riding a bike when he rode past the doctor and, "turned and fired two shots," police said at a news conference Friday.

ABC News' Meghan Keneally contributed to this story.