The "Walking Dead" star, who has played plenty of cops, told David Letterman on Monday's "Late Show" that he once busted a purse snatcher on his way home from work.
"Last Christmas, I was coming off the set, driving home with my dog Boss … and I heard a woman on the side of the road scream, 'Stop him! He stole my purse!'" Bernthal recalled to Letterman.
"I see a guy running down the street with this lady's purse, and it was Christmastime, and there was a guy dressed up like Santa Claus … he gets in front of (the mugger) and the guy with the purse barrels his shoulder right into Santa Claus and knocks him over … you do not do that to Santa Claus, man!"
Bernthal's tale goes on to include how he pulled his truck in front of the "perp" and flipped him over the vehicle, and how, in channeling one of his favorite TV shows -- "Cops" -- he risked getting himself in trouble for trying to make a citizen's arrest.
Bernthal, whose Deputy Shane bit the dust in Sunday's "Walking Dead" episode, will next star in TNT's cop drama "L.A. Noir," from original "Walking Dead" showrunner Frank Darabont.
