CHICAGO (CBS) — Chicago police were questioning a mother and her boyfriend about the brutal beating death of her four-year-old son.

Friday was Christopher Valdez’s birthday. Police say they found his lifeless body in a home in the 5100 block of South Trumbull Avenue in Gage Park.

Police say the boy may have been dead for several hours before they arrived at the house shortly after 2 p.m.

The child appeared to have died from “multiple blunt force trauma,” police said.

The boy was pronounced dead at Holy Cross Hospital at 3:10 p.m., according to the Cook County Medical Examiner’s office.

“I just don’t understand how anybody could do that. Just a shock to me,” the child’s great-grandfather, Santiago Valdez, told reporters.

LISTEN: WBBM Newsradio’s John Waelti reports

Contributing: Sun-Times Media Wire

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