Police say Martin Alvarado was babysitting the child for his girlfriend when a diaper change became necessary.
As Alvarado began the process, the toddler began to urinate on him. The Chicago Sun-Times writes, "according to investigators, the incident enraged Alvarado, who responded by repeatedly striking the boy.
Reports from the Cook County coroner say Edwin Eli O'Reilly died from “multiple blunt force injuries from child abuse.” The death was ruled a homicide, and Alvarado was taken into custody. During a taped interview, Alvarado incriminated himself in the death of the child.
NBC Chicago reports "a sibling of O'Reilly was taken into protective custody by the Illinois Department of Children and Family Services, which has had prior contact with the family." Alvarado faces a charge of first-degree murder.