Yellowstone's John Dutton (Kevin Costner) may not know the guy who attacked him, but we do. "Riggins" appears in a photograph — a mugshot, actually — during Ep. 3 of Season 4, titled "All I See Is You."

"He knows you," Mo (actor Mo Brings Plenty) says to the confused Dutton patriarch, who's holding a file with more information.

The Paramount Network program seems poised to introduce a new character soon, albeit one in Montana's state prison. Riggins is the guy who hired the militia to attack John, Kayce (Luke Grimes) and Beth Dutton (Kelly Reilly), as well as the ranch, but his motives are still unknown.

Actor Bruno Amato is the man photographed, as all but confirmed on his Instagram page. Amato is a veteran actor with more than 100 credits to his name. He's also a Navy veteran and a current candidate for the U.S. House of Representatives.

"This guy looks very familiar," he captions.

IMDB points to shows including Lucifer on Netflix, American Housewife on ABC and the Will & Grace reboot as Amato's recent credits. His 20-year resume also includes small roles on soap operas, Brooklyn Nine-Nine and How I Met Your Mother. The Bakersfield Californian refers to his service in the U.S. Navy, where he served as a torpedoman. Presently, the Democrat is trying to unseat Kevin McCarthy in the U.S. House or Representatives.

While not yet listed as part of the Yellowstone cast, there's further circumstantial evidence pointing to his involvement on Instagram and Twitter. The character of Riggins couldn't be more enigmatic, however — keep reading only if you don't mind a spoiler alert.

After the indigenous tribe is cleared as a possible attacker, and the Market Equities team seems clueless about who attacked the ranch, most started to look at Jamie Dutton and his birth father as potential planners. Neither John nor Kayce Dutton believe that's true, although Beth Dutton sure does, and promises she'll kill him one day for it. The slow unpacking of who hired the militia is the primary plot point driving Season 4 of the show, although hardly the only one.

On Thursday (Nov. 18), look for Ep. 2 of Dutton Rules: A Yellowstone and 1883 Podcast, in which the various threads will be untangled and laid out to see where the show may be headed. Find the podcast on Apple Podcasts and Spotify.

10 'Yellowstone' Facts You Probably Didn't Know

How big of a fan of Yellowstone are you? These 10 facts about the Paramount Network show are sure to stump even the most dedicated viewers. They're almost all about the cast members and their real-life passions and roles. John's kids? Beth's accent? Rainwater's guitar playing? Tate's spoilers? It's all part of this list of 10 Facts You Probably Didn't Know About Yellowstone.