Chicago police say they intercepted the man after he fired a shotgun into a park.
Alexander Podgorny, 29, now faces five felony counts of aggravated unlawful use of a weapon.
"I think of Columbine, I think of all the other mass shootings that we hear about nationwide, and this hits home," said Alderman Stephanie Coleman of Chicago’s 16th Ward. "To know that this could have been us, it devastates me, but then it also gives me comfort that we have men and women that are serving and protecting us."
Podgorny was arrested near Moran Park, located at 57th Street and Racine Avenue, after police responded to a ShotSpotter alert around 3:30 a.m. Thursday.
An arrest report obtained by FOX 32 from the Cook County Circuit Court Clerk states that police located Podgorny near his minivan. Police said his driver’s side and passenger side doors were open.
Documents state that in his pocket, Podgorny had a loaded semi-automatic handgun.
When police searched his vehicle, four other guns were recovered, including a shotgun and an AR-15.
All of those firearms were "readily accessible and ready to be fired" – according to Podgorny’s arrest report.
Plus, police said they found at least 300 spent shell casings of various calibers, over 1,000 rounds of ammunition, and handwritten notes that "contained incoherent rants and references to mass shooting events."
In his vehicle, officers also located a hatchet and a pruning saw, according to the arrest report.
Based on their discoveries, CPD alerted the FBI and ATF.
"All I can do is be grateful that no one was shot, that none of our children – that I’m not calling their parents or visiting their homes because they are no longer with us," said Coleman.
Chicago’s 16th Ward Alderman Stephanie Coleman said she credits ShotSpotter technology and officers' quick actions.
"They were able to find this person that could have done a heinous, heinous act of just hatred, discourse of divisiveness to our community," said Coleman.
Police said they recovered a FOID card from Podgorny and completed a Clear and Present Danger form.
According to his Facebook page, Podgorny studied at the University of Illinois.
Police say Podgorny currently lives in Woodridge. No one answered at Podgorny's listed address.
Requests for a statement from Podgorny’s father, who is an attorney, went unreturned Friday.
Podgorny appeared in bond court Friday and bail was set at $300,000 cash.
Podgorny – who police said does not have a prior criminal record – is due back in court Friday, Aug. 12.