BBC reports that Mr Fuentes, 45, died on Saturday in hospital after the ambush on Thursday night.
He was a contestant on the singing show in 2011.
His death comes 10 days after singer Christina Grimmie, who appeared on the US edition of The Voice, was shot and killed in Orlando, Florida.
The number of murders in Chicago this year is up 72% from 2015.
Mr Fuentes had been celebrating his birthday with friends on Thursday night, the local medical examiner's office said.
He was in his car on the street outside Tras Bambalinas, a performing arts school he ran for young people in south-west Chicago.
A gunman ordered him out of the car - when he refused, the gunman shot him three times in the head.
No arrests have yet been made.
Ms Grimmie, 22, was shot by a fan in Orlando as she was signing autographs after a concert. Her attacker then killed himself.