Brandon Graese, 26, of Delray Beach, grabbed a woman's purse then hopped in a silver getaway car driven by Amy Kaufman, 32, of Jupiter, according to police.
A Boynton Beach police officer followed the car to De Carie Street, not far from the Walmart, and arrested them at gunpoint.
The woman, Sherry Gross, 64, said her fingernail was torn off when a man grabbed her purse as she held it in her shopping cart.
The woman's husband, Edward Youngblood, 81, raced after Graese and tried to hit the car with his cane, police said. But as Graese jumped into the car, its open passenger door knocked Youngblood to the ground.
Kaufman is being held at the Palm Beach County Jail on $20,000 bail, while Graese is being held with no bail, records show.
In addition to one charge each of robbery by sudden snatching, Graese and Kaufman were each charged with aggravated battery of a senior.