A baseball player in the Dominican Republic was so upset with an umpire ... he attacked the guy with his bat AND helmet -- and video of the incident is INSANE.
It all went down Sunday ... when MLB Insider Hector Gomez says Elvis LeBron lost his mind during a tournament game over an ump's balls and strikes calls.
You can see in the footage, LeBron exchanged several words with the man behind the plate after one call ... and the conversation got so heated, LeBron was ultimately tossed from the game.