When their 4-month-old son wouldn’t stop crying, a New Jersey couple covered him with a comforter and went out for a smoke – only to later find that their baby had stopped breathing, prosecutors said Tuesday.

William Herring, 42, and Brianna Brochhausen, 22, were living at the Hilltop Motel in Springfield Township when they allegedly killed their son, Hunter, on Valentine’s Day, according to KTLA sister station WPIX in New York. They decided Hunter needed a “timeout” because he would not stop crying.

They put him on his stomach on a bed, pulled the comforter completely over him and left to smoke, investigators said. Hunter wasn’t breathing when they came back.

He was rushed to a local hospital, but he had minimal brain activity. Hunter breathed with the assistance of a respirator for several weeks and died on March 3 after life support was removed.

Herring and Brochhausen were initially charged with endangering the welfare of a child, but prosecutors upgraded the charges against them. They’re now facing murder charges in connection with their son’s death.

“The thoughtless actions of these individuals ended up costing a defenseless 4-month-old infant his life,” said Col. Patrick Callahan, the New Jersey State Police superintendent.