Updated

Police in Louisville say a 6-year-old boy has died of head trauma, four days after his mother's boyfriend allegedly assaulted him.

Louisville Metro Police say in a Facebook post that the boy, who hasn't been identified, was pronounced dead Monday morning.

Police spokesman Dwight Mitchell says the assault charge filed against 23-year-old Darrell Ditto after his arrest Friday has been upgraded to murder. Police initially responded Thursday to Ditto's residence regarding a report of a boy in cardiac arrest. The child was taken to the hospital with critical head injuries.

Jefferson County jail records do not list an attorney for Ditto. It's not clear whether anybody else has been charged.