An 86-year-old Illinois man with a concealed carry permit fired his weapon at an armed robbery suspect fleeing police last month, stopping the man in his tracks and allowing the police to make an arrest.

Law enforcement authorities described the man as “a model citizen” who “helped others avoid being victims” at an AT&T store outside Chicago where he witnessed the holdup. The man, whose identity was withheld from the press, prevented others from entering the store during the theft.

Police said the robber harassed customers and pistol-whipped one.

Since Illinois started granting concealed carry permits this year, the number of robberies that have led to arrests in Chicago has declined 20 percent from last year, according to police department statistics. Reports of burglary and motor vehicle theft are down 20 percent and 26 percent, respectively. In the first quarter, the city’s homicide rate was at a 56-year low.

“It isn’t any coincidence crime rates started to go down when concealed carry was permitted. Just the idea that the criminals don’t know who’s armed and who isn’t has a deterrence effect,” said Richard Pearson, executive director of the Illinois State Rifle Association. “The police department hasn’t changed a single tactic — they haven’t announced a shift in policy or of course — and yet you have these incredible numbers.”