Alex Blickem, of New Ulm, Minnesota, faces charges of aggravated battery causing great bodily harm, burglary, attempted first-degree murder and aggravated battery using a deadly weapon, Chicago police said Friday night.
He's accused of stabbing a man who was working out in the gym of his River North condo building early Thursday morning.
The attack happened just before 5:30 a.m. at a high rise near Wabash and Hubbard, Chicago police said.
SEE MORE: Intruder stabs man at River North condo fitness center
A resident said after the intruder got into the building, he went to the mailroom and damaged packages. Then he somehow got into the fitness center, where he stabbed a 38-year-old resident who was exercising there.
The victim was rushed to the hospital with serious injuries, but was later stabilized. Chicago police arrested his alleged attacker and recovered a knife.
In a letter to residents, the building's property manager said they are "reviewing all security conditions of the building" and "will enact whatever steps necessary to safe guard River Plaza and all of its residents."
Some residents said they feel very unnerved by how the alleged attacker was able to get into the building and continue on to the fitness room.
The video featured is from a previous report.
EDITORIAL NOTE: Police originally said Blockem was from New Ulm, NM, but have since corrected to say he is from New Ulm, MN.