A suburban father-of-two was fatally shot while leaving a wine tasting in Chicago’s Millennium Park Saturday following an alleged argument with another man, police confirm to PEOPLE.

While Peter Fabbri, 54, of Berwyn, Illinois, lay bleeding on the ground, his sister, Shelly Fabbri, chased down the suspect, who had jumped on a bike, helping police to bring him into custody, Peter and Shelly’s brother, Bruno Fabbri, tells PEOPLE, relaying Shelly’s account.

“Our family is devastated,” says Bruno.

Fabbri, the father of two adult daughters, died just before 6 p.m. Sunday at Northwestern Memorial Hospital, according to the Cook County Medical Examiner’s office.

Authorities are questioning the suspect, who was taken into custody Saturday night, a spokeswoman for the Chicago Police Department tells PEOPLE. Detectives are still investigating the shooting and have not released the suspect’s name.

The trouble began after Fabbri left a wine tasting with his sister and girlfriend on Saturday night near Millennium Park, one of Chicago’s most popular destinations. He was walking about ten feet behind the two women, says Bruno.

Near the intersection of East Monroe Street and South Michigan Avenue, Fabbri allegedly got into a verbal altercation with another man, the police spokeswoman says.

“The altercation turned physical and the offender pulled out a handgun and shot him,” says the spokeswoman. Police have not said what they were arguing about.

One witness told CBS 2 that Fabbri and the other man were allegedly arguing over politics.

However, Bruno says, “That doesnâ€™t sound like my brother. He wasn’t into politics that much.”

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When gunshots first rang out, says Bruno, “My brother ran up to my sister and said, ‘Run! I’ve just been shot!’” Bruno says.

He’d been shot in the torso, and as his sister cried for help and called Bruno, the suspect allegedly shot Fabbri in the head, says Bruno.

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“The next thing I hear is her running and breathing real hard,” Bruno says.

Shelly had begun chasing the suspect, who had taken a bicycle and tried to get away, says Bruno.

Fabbri was rushed to the hospital, says Bruno. His family took him off life support on Sunday.

They are left “with a broken heart and tears in our eyes and down our faces,” his niece, Nina Parks, wrote on a GoFundMe page she set up to help pay for his funeral expenses.

She described her uncle as “a huge hearted man and was always there for anyone if he could be.”

Fabbri worked with Bruno as a home improvement contractor. “He was very caring,” says Bruno. “If a customer was short on money, he would help them. He would give you the shirt off his back and if he didnâ€™t have a shirt, he would make one for you.”

His brother attended the wine tasting mostly because he loved Lake Michigan, near the park. “He thought it was beautiful,” says Bruno.

Bruno says he and his family still cannot believe Fabbri is gone. “It’s overwhelming,” he says. “The violence has to stop.”