Nashville mother asked a friend to babysit her 3-year-old. He's charged in the child's killing.

A Nashville man was arrested Thursday in the killing of a 3-year-old girl he babysat on Saturday.

Metro Nashville police say Christopher J. Riley, 26, of Bellevue, is charged with first-degree murder and aggravated child abuse in the death of the child, Laylani Rose Stevens.

The young girl suffered extensive head and other internal and external injuries, authorities say.

According to police, Laylani's mother brought her late Saturday night to St. Thomas Hospital West, from where she was immediately transferred by ambulance to Vanderbilt Children's Hospital.

She died Sunday afternoon at Vanderbilt.

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Based on detective's investigation, police determined the child's mother was unable to arrange another babysitter for the child and asked Riley, a friend of hers, to watch the girl while she was at work Saturday afternoon and evening.

When the woman returned to her home on U.S. 70 around 10 p.m. Saturday, she found Laylani unresponsive. She said the child was uninjured when she left for work.

Police say Riley told the woman that Laylani was injured by falling, though doctors found her extensive injuries to be inconsistent with falling.

Riley was arrested Thursday afternoon after arriving at the police department's youth services division with his attorney. Bond information wasn't immediately available.

Reach Natalie Allison at nallison@tennessean.com. Follow her on Twitter at @natalie_allison.