I know how this happened. There is a glitch in the ability called "Storm, Earth, and Fire". The "Fire" buff has a chance of two glitches, for the monk to become a 'friendly' unit to all enemies but he, however, can still damage enemies, making him invincible. Or, the 'Fire' can transform his target into the Monk.
“Marines I see as two breeds, Rottweilers or Dobermans, because Marines come in two varieties, big and mean, or skinny and mean. They're aggressive on the attack and tenacious on defense. They've got really short hair and they always go for the throat.”
― R. Adm. Jay Stark