The man suspected of killing Adrian Peterson's 2-year-old son last year has been ARRESTED -- after officials say he kidnapped the child's mother and attacked her.

The suspect is 28-year-old Joseph Robert Patterson -- who was charged with murder and child abuse for allegedly beating Peterson's son Tyrese to death in October 2013.

Patterson had been free on the murder charge on $750k bond -- and was under instructions to NOT contact the child's mother or anyone else in the family.

But Patterson apparently ignored the instructions -- and kidnapped the child's mother. Cops in Sioux Falls, South Dakota say they responded to a call early Tuesday morning.

Patterson was apprehended -- and has since been charged with kidnapping, two counts of aggravated assault, interference with emergency communications and third-degree burglary.

He's due in court later today.