Oklahoma City Police just dropped dramatic body cam footage ... showing the intense moment cops shot an armed man in a fatal incident that began as a mental health call.
The clip's a tough watch -- It shows Brandon Lena, in distress, walking around with a pistol outside his house near Tinker Air Force Base.
Despite officers’ efforts to calm things down, it escalates quickly, ending with Lena’s death in the street.
Watch the video ... Officers James Doran, Joshua Geerdes and Jimmy Hatfield introduce themselves as Crisis Intervention Team members ... and they beg Lena to drop the gun. He's repeatedly warned -- but Lena points his gun straight at them.
Officers fire less-than-lethal 40mm projectiles in an effort to subdue Lena, striking him in the torso ... but he’s still aiming his gun at the officers. They shoot more less-than-lethal rounds in a futile attempt to defuse the situation.
Officers are then heard firing multiple rounds of gunshots at Lena ... instantly killing him.
OKCPD says all 3 officers are on routine administrative leave while the August 2 shooting is officially investigated.