SIERRA VISTA, Ariz. — A former Sierra Vista police officer who resigned after it was discovered that he was having a sexual relationship with a confidential informant has killed himself at his home, authorities said.

Michael Mitchell, 39, resigned from the Sierra Vista Police Department last year after an internal investigation revealed that he removed evidence from a crime scene to protect an informant he had a sexual relationship with, reported The Sierra Vista Herald ( ).

Police found Mitchell at his Marana home Monday afternoon while responding to a report of an unresponsive male. Mitchell was pronounced dead at the scene.

Authorities haven’t released details of Mitchell’s death, but Marana Police Sgt. Chris Warren said all evidence appears to indicate suicide.

“Despite the circumstance that he left the police department under, he was a human being that had family and friends,” said Sierra Vista Police Chief Adam Thrasher. “Our hearts go out to everybody that cared for Mike.”

Mitchell began working for the Sierra Vista Police Department in 2004 and served as the department’s lead K9 handler for years. He was involved in the investigation and arrest of several drug dealers and other criminals.

“He was a very, very effective law enforcement officer,” Brian McIntyre, a Cochise County attorney, told the Herald last month. “There is no other way to characterize it. He put together very good, very strong cases.”

Mitchell’s resignation came after Sierra Vista police, acting on a tip from a man arrested on burglary charges, discovered text messages between the former officer and a confidential informant indicating they had a sexual relationship. Police also say Mitchell removed the woman’s cellphone from a vehicle that was seized as evidence.

In an interview with police, the informant denied ever having been paid for information she provided to Mitchell.

At least 17 pending criminal cases that relied on testimony from Mitchell had to be dismissed once the investigation into his misconduct began. The police department also reviewed all of Mitchell’s previous cases but found no misconduct.

Information from: Sierra Vista Herald,