The suspect behind the tragic slaying of renowned cardiologist Mark Hausknecht, who once treated George H.W. Bush, is a man with a 20-year grudge against the doctor, Houston police said. Joseph James Pappas, 65, was identified as the suspect, and a warrant has been issued for his arrest. Pappas’ mother died in surgery while she was Hausknecht’s patient over 20 years ago, said Houston Police Chief Art Acevedo. Hausknecht, who is known for treating Bush for an irregular heartbeat, was killed while riding his bicycle to work. “The suspect was on a bicycle as well. Rode past the doctor, turned and fired two shots. The doctor immediately went down,” Houston Police Executive Assistant Chief Troy Finner said after the incident. Acevedo said police searched Pappas’ home and found evidence connecting him to the crime, but declined to offer more details. “We believe that this man is absolutely the killer,” Acevedo told the Houston Chronicle. No one has seen Pappas for more than 36 hours and police believe he is suicidal.