Police said Thomas has a valid firearm owner's identification card and a concealed carry permit, WGN reported.
>> Florida school shooting survivors return to campus
The AR-15 has been at the center of a gun control debate in the aftermath of a mass shooting at a Florida high school on Feb. 14 that left 17 people dead, including 14 students. The attacker used an AR-15, police said. Nikolas Cruz, 19, has been charged in the shooting at Marjory Stoneman Douglas High School in Parkland.
Thomas said the AR-15 was his “weapon of choice” for home protection.
“It's light, it's maneuverable. If you train and know how to use it properly, it's not dangerous,” Thomas told WGN.