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.

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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.

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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

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Contributing: Sun-Times Media Wire