Joseph Guardia, of Melrose Park, was arrested and charged with attempted murder and arson, Chicago police announced Sunday.
Multiple reports say the victim, Joseph Kromelis, is a well-known member of the city's homeless community and is often seen roaming with downtown area. Many have nicknamed him "Walking Man."
Police said Guardia is the man who allegedly doused Kromelis in flammable liquid and lit him on fire early Wednesday morning as he was lying on the ground at the intersection of Kinzie and Lower Wabash.
Kromelis suffered burns to nearly half his body and was taken to Northwestern Memorial Hospital, where he is listed in critical condition.
A security officer from a nearby building used a fire extinguisher to put the fire out.
A Surveillance image released by police showed a man running from the scene west on Kinzie.
Advocates for the homeless say living on the street can be dangerous.
"This is really not the first or second time something unfortunate like this has happened," said Ali Simmons, with Chicago Coalition for the Homeless.
In May 2016, Kromelis was attacked by someone wielding a bat. He recovered after weeks in the hospital.
Activists say many more crimes against the homeless go unreported.
"We are dealing with things now, with our Texas families. We lost kids. And you have the nerve to set a homeless man on fire. How can you live with yourself?" said Michael Airhart, with Taste for the Homeless.
A $1,000 reward was offered by both Michael Airhart and Andrew Holmes for information leading to an arrest in this case.