A convicted felon is due back in court Friday after allegedly sucker-punching a 91-year-old man in Chicago earlier this week in what police are calling a random and “brutal” attack.

Police Sgt. Michael Bazarek said he was driving around the city’s Chinatown neighborhood on his way to get a cup of coffee around lunchtime Tuesday when he witnessed the shocking incident.

“My reaction was -- I have to do something. I’m a policeman,” he told reporters after cornering the alleged attacker, identified as 45-year-old Alexander Taylor.

Bazarek said Taylor was “acting out, waving his hands in a violent manner, [making] gestures and ranting going from gibberish to unintelligible comments, talking at the sky, talking at the sidewalk and frightening people” before turning and striking Yen Jit Wong.

Bazarek added the attack happened “without provocation,” according to the Chicago Sun-Times, and police took the suspect into custody without incident after backup officers arrived.

The punch caused Wong to suffer bleeding on his brain, FOX32 Chicago reported. As of Wednesday, Wong was moved out of the Northwestern Memorial Hospital’s intensive care unit, but he still cannot speak, according to FOX32.

“Why would you do something like that to an elderly person like this, why?” said the man's son, James Wong.

Wong has 15 grandchildren, and one of his five great-grandchildren, Lauren Chiu, described Wong as a friendly person who offers plenty of hugs.

Taylor is facing multiple charges stemming from the incident, including aggravated battery to a victim older than 60, police said.

The Chicago Tribune reported Taylor previously has been convicted for hitting a senior citizen in 2008 and for attempted murder in 1998, racking up nearly a dozen years in prison over the last two decades.