MEMPHIS — An ex-con accused of fatally shooting a police officer who interrupted a drug deal turned himself in Monday, ending an intensive two-day manhunt, authorities said.Tremaine Wilbourn, 29, is accused of killing officer Sean Bolton on Saturday night, after the officer approached a car along a street that had been known for years as a quiet oasis amid a troubled neighborhood.Wilbourn was with his family and an attorney when he turned himself in.“I think he felt the walls closing in and thought it would be in his best interest to turn himself in,” Memphis Police Director Toney Armstrong said Monday.Armstrong spoke briefly to Wilbourn and the suspect told him: “I want you to know that one, I’m not a cold-blooded killer and two, I am not a coward.”Armstrong had used that word to describe Wilbourn during the manhunt.On Saturday night, police said Wilbourn was a passenger in a 2002 Mercedes Benz that was parked illegally in the southeast Memphis neighborhood.