A South Side man wedged a loud radio in the doorway of his home before he broke his girlfriend’s bones and brutally murdered her during an argument over a bus pass, Cook County prosecutors said.

Ronald James, who has a previous conviction for an aggravated battery of a transit employee, was observed fighting with Katrina Rogers near a bus stop at 51st and Calumet on Sept. 13, assistant state’s attorney Farrah Brass said at his bond hearing Wednesday.

Eventually James, 41, dragged a screaming Rogers back to his house in the 5000 block of South Prairie Avenue, Brass said.

A witness allegedly saw James place a radio in the doorway and turn up the volume to drown out any noise before he went back in.

Several hours later, James called emergency personnel, who found a dead Rogers in rigor mortis and partially clothed at the bottom on the basement stairs, Brass said.

James told the officers the couple had been attacked by a group of individuals when they had gone down to the basement to clean up a half-hour before, Brass said.

When James was taken to the police station, he allegedly told an officer that he and Rogers had “gotten into it” following the mob attack.

But detectives found blood throughout the house, disputing James’ account that he and Rogers were ambushed outside, Brass said.

Rogers’ blood was also found on a bicycle seat that was in a bedroom and on a shirt and shoes that were found in a nearby dumpster — proving that James tried to clean up the murder scene and dispose of the evidence, Brass said.

James has a lengthy rap sheet, including aggravated battery to a police officer and several drug-related convictions.

James, who angrily mumbled during Wednesday’s court hearing, was ordered held in lieu of $2 million bail.