It happened near the intersection of A and East Somerset streets just before 8 p.m.
Police told Action News a 35-year-old man approached a homeless man on the street and attempted to rob him with a BB gun.
That's when the homeless man reportedly pulled out his own gun and shot the suspect in the back.
He then fled the scene, according to police.
Officers say the would-be robber was taken to an area hospital in critical condition.
No charges have been filed at this time. Police have not released any further information on the alleged shooter.
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