EXCLUSIVE

NY Giants linebacker Jonathan Casillas should've been a running back -- because it took 5 SECURITY OFFICERS to bring him down during a violent casino clash back in 2012. 

We've been making calls for days trying to gather all the info about this crazy video -- and though the details are scarce, here's what we know ... 

-- It happened at 6 AM on May 12, 2012 at the Harrah's Casino in Atlantic City

-- Before the video begins, Casillas was pissed ... and walked outside to cool off. You see him throw a potted plant across the valet area. 

-- Casillas went back inside and was confronted by several security officers. Things get testy, Casillas tucks his chain, a security officer shoves Casillas and Casillas shoves back

-- Things went nuclear from there. 5 guys tried to take Casillas down. They struggled, but eventually got him to the ground. He was handcuffed and detained. 

-- Two Atlantic City PD officers were involved. 

We've reached out to the Atlantic City PD to find out if criminal charges were filed. One source connected to the incident says a civil suit was filed ... but unclear who filed it or if it's still active. 

Multiple attempts to reach Casillas and his reps were unsuccessful.