A cardiologist who once treated former President George H.W. Bush was fatally shot by a fellow bicyclist Friday while riding through a Houston medical complex. The shooting happened around 9 a.m. as Dr. Mark Hausknecht was going northbound through the Texas Medical Center, said Houston Police Executive Assistant Chief Troy Finner. “The suspect was on a bicycle as well. Rode past the doctor, turned and fired two shots. The doctor immediately went down,” Finner said. Hausknecht treated Bush in February 2000 for an irregular heartbeat after the ex-president complained about lightheadedness while visiting Florida.