MERIDIAN -- A former sergeant with the Washington County Sheriff's Office has pleaded guilty to having a sexual relationship with a 15-year-old Meridian boy.

Michael Alexander, 46, met the teenager on Grindr, a gay hookup app. Prosecutors said he traveled to the Idaho to have sex with the boy at least twice in 2015.

Alexander's lawyer said the former deputy did not know the teen was underage. The boy told Alexander he was 18 turning 19, and a college student at Boise State.

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The defendant was arrested in March 2016 after the teen's mother found inappropriate messages between Alexander and her son and called police.

He pleaded guilty to felony lewd conduct with a child last Friday. The charge is punishable by up to life in prison.

Sentencing is set for May 8.