Man shot in the head while walking with family on Michigan Ave.

UPDATE: The 54-year-old man who was shot on Saturday night near Chicago's Millennium Park has died. Read more:

CHICAGO -- A 54-year-old man was walking with his family near Millennium Park Saturday night when he was shot in the head. The family of Peter Fabbri said now he’s brain dead and on life support.

His sister Shelly said a group of people – some of them on bikes - approached the family as they were walking down Michigan Avenue. She said there was an argument, a fight, and then gunshots.

“My brother's like, ‘Shelly, just get away,’” she said. “I just got caught, then another guy came back and shot him through his head.”

Shelly said she tried to stop the killer from getting away, chasing him into the street and trying to hold on to his bike, until another accomplice hit her and she fell to the ground.

Police surrounded the high traffic area quickly and believe they have the shooter in custody. They're looking for additional suspects involved in the incident.

Fabbri was taken to Northwestern Memorial Hospital in critical condition and is on life support, according to his family.

His niece said it was shocking something so tragic could happen to a family walking down the street, especially so close to Millennium Park.

“Is this what we’ve become as a city, that we allow bad guys to feel comfortable enough to shoot someone in the heart of our city?” she asked.