HOUSTON — Authorities on Wednesday identified a man who they believe gunned down one of former President George H.W. Bush's doctors last month as the son of a woman who died while the doctor was operating on her more than 20 years ago.

Houston police Chief Art Acevedo said at a news conference Wednesday that the suspect, 62-year-old Joseph James Pappas, should be considered armed, dangerous and possibly suicidal. Authorities said he may have been seeking revenge for his mother's death.

Joseph James Pappas Houston police

"There was a lot of planning that went into this. There was a lot of planning and, sadly, some skill," Acevedo said of the attack on Dr. Mark Hausknecht, who was gunned down July 20 while riding his bike to work. Authorities say the shooter rode past Hausknecht before turning around and firing.

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Acevedo said Pappas is white and very fit and that he likely has his 10-speed bicycle, which he rides "extensively and almost exclusively."

In 2000, Hausknecht treated Bush for an irregular heartbeat after the ex-president complained about lightheadedness.

A tip on Tuesday led police to suspect Pappas, the chief said, though he didn't elaborate as to the nature of the tip. Acevedo said police searched his home at 4 a.m. Wednesday and found evidence that ties Pappas to the killing, but he declined to elaborate as to the nature of the evidence.

Acevedo said Pappas hasn't been seen in 36 to 48 hours. He said the last anyone had heard from Pappas was in a Tuesday morning text message in which Pappas wrote that he was going to kill himself.

Anyone who sees Pappas is asked to call 911.