The man who allegedly beat Adrian Peterson's 2-year-old son to death was just charged with second degree murder ... TMZ has learned.
Joseph Patterson was charged with second degree murder and 2 counts of first degree manslaughter, as well as aggravated battery of an infant. He was also charged with felony child abuse.
Patterson, who was dating Adrian's baby mama at the time, was supposed to be caring for the child while she was away.
Second degree murder carries a mandatory life sentence in South Dakota.