A St. Paul man has pleaded guilty to the unintentional murder of his girlfriend’s 3-year-old son in exchange for a 15-year prison sentence.

Alontae Kaypre Butts, 25, entered an Alford plea in Ramsey County District Court on Thursday, acknowledging prosecutors had enough evidence to convict him of second-degree murder during the malicious punishment of 3-year-old Levi Gardent Jr.

Gardent died on Jan. 15 of blunt-force trauma that tore his bowel and caused his liver and diaphragm to hemorrhage, prosecutors said.

Gardent, his brother, 6, and sister, 2, were all in Butts’ care while their mother was at work.

Butts also entered an Alford plea to the malicious punishment of Levi’s 2-year-old sister, who suffered significant abdominal trauma but survived her injuries.

District Judge Robyn Millenacker will sentence Butts in June.

According to the complaint, Gardent’s mother called 911 after finding him not breathing about 4 p.m. on Jan. 15. Medics transported him to Children’s Hospital, where bruises were found “all over” his body. He was in cardiac arrest and died shortly after.

Butts allegedly told police several stories about the boy’s injuries.

The boy’s 6-year-old brother told authorities that Butts choked his mother and all three children in the family and stomped on the toddler.