It's almost beyond words ... a freshman at a South Carolina high school posted a photo of himself wearing a mask and holding what looks like an assault rifle with the caption, "Round 2 of Florida tomorrow."

The 9th grader is now in custody after an alarmed parent notified authorities and sent along the Snapchat pic.

Deputies descended on the home of the student, who told them the post was a joke. Law enforcement found the gun -- an airsoft rifle -- and after a search of the home determined the student had no access to firearms.