Shia LaBeouf, in real life, where he doesn’t kill for sport or eat human bodies. (Markus Schreiber/AP)

We all know that Shia LaBeouf is the star of the “Transformers” movies, former boyfriend of the now-married Carey Mulligan and a guy who may, if provoked, throw coffee at a photographer and run away.

But did you know that Shia LaBeouf is ... a cannibal?

Well, of course you didn’t know that for a fact because it’s not true. I repeat, for the sake of clarity: Shia LaBeouf does not eat people. But in recent days, a patently absurd, thoroughly random and extremely catchy song that suggests the “Disturbia” star feasts on flesh has gone viral online. This is the story behind it.

L.A. songwriter Rob Cantor, 28, is the guy who wrote the ridiculous ditty about “actual cannibal Shia LaBeouf,” who is “living in the woods, killing for sport and eating all the bodies ” He says he penned the track last year “inspired by nothing but the sheer silliness of imagining Shia LaBeouf, face and clothes smeared with half-dried blood, terrorizing helpless victims in a dark wood.”

In an e-mail exchange today, Cantor — who writes music for TV, films and commercials as a freelancer and also sings and plays guitar with the indie rock band Tally Hall — explained that he originally hoped Funny or Die would want to use the song in a video featuring the actual LaBeouf. But that didn’t happen.

“Then it just sat on a hard drive for a year,” he says. “Then I posted it to my online portfolio, and a fan of the band discovered it and tweeted about it. Then it just caught fire.”

A few blogs — including Boing Boing — posted items about the song a couple of weeks ago. Then earlier this week, Buzzfeed, that resource for all sharable online minutiae, posted an animated clip (embedded above) that is set to the song and was created by YouTube user namefriend. Now the Shia LaBeouf Cannibal song is officially a thing. The actor hasn’t commented on it yet, but when he starts doing more press for his next film, “Lawless,” perhaps he will.

Cantor says he’s not a LaBeouf superfan. His main reason for deciding that Sam Witwicky should be musically described as brandishing a knife and living in the shadows? “It was more that his name, when whispered really intensely, just made me giggle.”

Apparently he’s not alone. If you want a copy of the Shia LaBeouf song so you can listen to it while working out — because pretending you’re running from a bloodthirsty Shia LaBeouf will motivate you to keep running on the treadmill, right? — it can be downloaded for $1 on Cantor’s Web site.