Ex-WWE superstar Marty Jannetty may have confessed to murdering someone when he was 13 years old in a bizarre social media post ... and now cops are investigating.

The former member of the tag team "The Rockers" told a story on Facebook about trying to buy weed from a man who worked at a bowling alley in his home town when things went awry.

"I was 13, working at Victory Lanes bowling alley buying weed from a f** that worked there ... and he put his hands on me ... he dragged me around the back of the building ... you already know what he was gonna try to do."

Jannetty continued, "That was the very first time I made a man disappear. They never found him. They shoulda looked in the Chattahoochie River."

By the way, Jannetty is 60 years old -- so the alleged incident would have taken place around 1973.

Now, the Columbus Police Dept. in Georgia tells us straight up, "We are going to look into this."

In fact, a spokesperson from the homicide/cold case division says, "The first step will be seeing if we have any missing persons or unidentified remains cases that match the limited information in the post."

The CPD notes that they have "several current active homicide investigations underway and they will have to remain the priority" -- so, it won't be an all hands on deck situation right now.

We've reached out to Jannetty for comment several times -- but haven't heard back. The Facebook post has since been removed from his page.

Jannetty was huge during the WWF's run in the '80s and '90s -- teaming up with Shawn Michaels on The Rockers ... one of the most popular tag teams of the era.

Jannetty went on to become the WWE Intercontinental Champion and Tag Team Champion.