Man allegedly threatened to shoot at people at Island Lake bar, hit patron with shotgun

A man threatened patrons in an Island Lake bar that he would “blow all their heads off,” left to load a gun inside his truck and then used the weapon to hit a man who tried to stop him from returning, authorities allege.

Thomas Garrison, 51, who has home addresses listed in court and jail records in both Rockford and Huntley, made an initial court appearance Friday and was detained in the county jail pretrial.

In arguing for Garrison’s detention, Assistant State’s Attorney Garrett Miller told Judge Cynthia Lamb that Garrison is dangerous and poses “an immense risk” to the alleged victims and the community.

Garrison is charged with possessing a Maverick 88 12-gauge shotgun with a defaced serial number; he’s also charged with possession of a firearm with a revoked Firearm Owner’s Identification Card, conspiracy to commit aggravated battery in a public place and disorderly conduct, according to Lamb and the criminal complaint filed against Garrison in the McHenry County court.

Police responded to a call at Mavericks Brew Pub at 1:31 a.m. Friday, the complaint said. Miller said the incident began when a woman at the bar rejected Garrison’s “unwanted advances” and others defended her and removed Garrison from the bar. He allegedly threatened to “shoot their heads off” and then was seen going back to his pickup truck and loading the firearm, Miller said.

As Garrison walked back to the bar with the loaded gun, a man tried to stop him, Miller said, leading to an altercation in which Garrison pistol-whipped the man, causing “deep lacerations to the back of his head.” The man was able to get the gun away from Garrison, unload it and hold it until police arrived, Miller said. The prosecutor also said Garrison has a conviction, making it illegal for him to possess a firearm, though Garrison’s public defender raised questions about that.

“This is as egregious and belligerent as we can get,” Miller said. “By the grace of God someone else intervened.”

But Assistant Public Defender David Giesinger argued for Garrison’s pretrial release with conditions that would allow him to start a new job this week. Giesinger said prosecutors’ claim that Garrison “was approaching the bar with the gun is a misstatement.”

Geisinger said the man who intervened saw Garrison loading the gun inside the pickup truck and the “physical altercation happened at the truck. The struggle occurred at the truck. He was not advancing toward the bar as the proffer says.”

Regarding Garrison’s legal history, Giesinger said Garrison previously pleaded guilty to a misdemeanor and was sentenced to probation. Winnebago County court documents show Garrison pleaded guilty on Feb. 27, 2023, to a battery/causing bodily harm, a Class A misdemeanor. He was sentenced to 18 months of probation which has been completed, records show.

“People getting drunk in a bar making an advance toward a woman happens every weekend in McHenry County,” Giesinger said, adding alcohol was involved, Garrison denies having a loaded gun and has said he was attempting to leave the bar.

Miller rebutted, saying Garrison made a threat, a “conscious decision” to go to his truck and load a shotgun, and the gun had a serial number removed. This was “an extremely heightened situation, not normal,” Miller said.