Sheriff’s deputies arrested a Florida man Sunday on suspicion of beating his 7-year-old stepson to death and threatening his three siblings until one of them struck the boy, according to the Hillsborough County Sheriff’s Office.

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Jack Junior Montgomery, 31, called investigators to a Masters Inn hotel room Saturday morning after he said he was unable to wake his stepson, Brice Russell. He told investigators that Brice hit his head after Montgomery threw him onto a bed when he tried to sneak out to get a cookie, according to an arrest affidavit obtained by WFTS.

"Montgomery said that Brice hit his head on the headboard when he threw him onto the bed, but said that he was fine after that," WFTS reported.

A medical examiner, however, determined that Brice suffered a number of injuries that "require a greater amount of force than those that would be sustained during a fist fight regardless of whether or not the assailant was a juvenile or adult," according to an arrest report obtained by the Miami Herald.

Montgomery was caring for Brice and his siblings while their mother, Donya Shenita Russell, was at work, according to deputies. Brice’s siblings told authorities they woke to hear their brother crying as he was being thrown around the room.

“Detectives determined that Montgomery had punched the child in the face, mouth and stomach with a closed fist, threw the victim around the hotel room and shoved his face into the carpet,” deputies said in a news release.

Authorities said Montgomery threatened to beat Brice’s siblings if they did not join the attack. In fear of Montgomery, one child hit Brice, according to deputies.

“Ultimately, the children saw Montgomery pick Brice up by the leg and (throw) him against a shelf along the wall,” deputies said. “The children told detectives they saw blood coming from his nose and mouth and that their brother never woke up after that.”

Medics with Hillsborough Fire Rescue said Brice was cold to the touch when they found him and starting to show signs of rigor mortis, the Herald reported. He was pronounced dead at the hotel room about 10 minutes after Montgomery called authorities.

It was the second time in less than 24 hours that deputies were called to Montgomery's hotel room, according to the Herald. An employee at Masters Inn called police just after midnight Saturday after a guest reported hearing a man yell "beat the kid," and "push the kid over here," among other things, the newspaper reported.

A deputy showed up at Montgomery's room, but the 31-year-old claimed the shouts were nothing more than loud music he had been playing. He pushed open the hotel room door wide enough to show the children sleeping on a bed, the Herald reported, and the deputy left.

Deputies arrested Montgomery Sunday on charges of first-degree murder, aggravated child abuse and two counts of child abuse. He remained jailed Tuesday.