LEAVENWORTH, Kan. - A Leavenworth man was charged Tuesday with killing his girlfriend's four-year-old son. Jason Lee Jones, 33, was released from prison in May for aggravated assault, but now he's back behind bars charged with murder.

Leavenworth County Attorney Todd Thompson said Jones shook, tortured and beat 4-year-old Gabriel Rivera, causing the boy's death. Investigators said Jones was watching Rivera and his own 11-year-old son while Rivera's mother was at work Sunday morning.

Police said the boy was taken to St. John's Hospital about 8:30 that morning and pronounced dead an hour later. Rivera's mother didn't want to talk about her son's murder, but Jones' mother said her son didn't do anything and insists the four-year-old was hurt by falling down the stairs.

Thompson said the child was killed by some type of force or trauma and he said this isn't the first time Jones has been accused of hurting a child.

"We had dealt with him in other matters that I can't really disclose, but it is my information that he has had parenting classes and things of that nature due to a history of child abuse," Thompson said.

Jones also has a long criminal history. According to court records, Jones has three aggravated battery charges, one aggravated weapons charge and two criminal threat charges. He also served more than two years in prison for aggravated assault and was released several months ago.

The mother of Jones' 11-year-old son, who did not want to be identified, said Jones is a very dangerous man.

"I think he needs to pay the price for everything he has done to everybody," she said.

Jones' bond is set at $750,000 and is expected back in court on Friday.