A Flathead Valley man accused of injuring his newborn during a drunken Christmas Eve argument with his girlfriend pleaded guilty earlier this month to criminal endangerment.

Joseph Richard Riggs changed his plea before Judge Dan Wilson in Flathead County District Court on July 6. He pleaded not guilty at his January arraignment, but struck a deal with the County Attorney’s Office in mid-June.

Under the terms of the agreement, prosecutors will recommend a deferred three-year sentence for the felony charge in exchange for the guilty plea.

Wilson set sentencing for Aug. 17.

Flathead County Sheriff’s Office deputies arrested Riggs after following up on a 911 hangup originating in a home along Montana 40 near Columbia Falls, court documents said. Riggs’ girlfriend later told authorities that the two argued after he became drunk.

As she prepared to leave, she placed the couple’s one-month-old into a car seat unstrapped, court documents said. Attempting to hold them up, Riggs allegedly grabbed the car seat, sending the child out of it.

The child subsequently struck his head on a propane tank, court documents said. A CT Scan at an area hospital revealed the child suffered a subdural hematoma, or bleeding in the head.