A 52-year-old Illinois man has been charged with involuntary manslaughter for an incident last month that killed a 9-year-old boy at a Chicago Transit Authority station.

Police announced the arrest of Michael Korosa on Monday, WMAQ reported.

Investigators said 9-year-old Elijah Flores was exiting a train with his mother’s boyfriend shortly after 11 a.m. on August 10. The boyfriend was arguing with two other men at the Clinton Station when the other two men began chasing the boyfriend and the child from the platform.

The 22-year-old boyfriend picked up the child because “he was not keeping up,” a police report said. One of the two men then hit the boyfriend in the back with an “object,” knocking him and the child down a flight of stairs. The boyfriend landed on top of Elijah, knocking him unconscious and fracturing his skull.

The boy was taken to Lurie Children’s Hospital in critical condition and died six days later. The Cook County Medical Examiner’s Office said the boy died from blunt force injuries to the head and the cause of death was homicide.

Investigators identified Korosa as one of the two men arguing with the boyfriend.  He was initially charged with murder when he was arrested on Sunday, WGN reported, but the charges were downgraded on Monday.

Korosa was also charged with aggravated battery.

Police did not say what the men were arguing about or whether they had identified the second man involved and if he would also face charges.