The man saw two males park a white Honda Civic in the mall parking lot around 1:40 p.m., Lt. Greg Hurlbut said.
One of the Honda's occupants looked into the interior of a parked vehicle but the two suspects left when the parked car's alarm sounded, Hurlbut said.
The citizen called police and followed the Honda as it parked again at the mall and the two males entered a green Honda Civic and drove away, Hurlbut said.
The citizen followed the green Honda as he spoke to a police dispatcher, and an officer then tried to stop the Honda as it left the parking lot, Hurlbut said.
The car fled and the officer followed the Honda as it drove through the downtown area. He stopped the pursuit when the Honda began passing other cars, Hurlbut said.
The Honda drove through a stop sign and collided with a full-size pickup truck at the intersection of Washington Street and Travis Boulevard, Hurlbut said.
Two juvenile males from Richmond who were in the car were immediately captured and arrested on suspicion of vehicle theft, possession of stolen property and conspiracy, Hurlbut said.
The suspects were injured in the crash and taken to a trauma center. One was treated and released and booked into juvenile hall. The other remains in serious but stable condition at the hospital, Hurlbut said.
Police are thankful the citizen assisted them in the case, Hurlbut said.