A man wielding a chainsaw in an assisted-living facility was shot after a tense standoff with police .. and, the whole showdown was caught on dramatic body cam footage.

Video of the incident -- which happened back in December -- captures Daniel H. Escalera, an Indiana man, who was at River Glen of St. Charles assisted living facility in Illinois, revving the chainsaw as officers arrive on the scene.

The responding officer repeatedly tells the man to drop the chainsaw, as Escalera says he just wants to see his wife ... while trying hard to get it started. Eventually, he's able to get the tool going -- which is when the officer tases him.

The Taser doesn't stop him ... and, Escalera pops back up with the saw, running through a cafeteria and into a hallway and shrieking, while other officers swarm the assisted-living facility.

In another body cam clip, Escalera rushes at an officer with chainsaw in hand ... hitting the officer with it and dropping it before running down the hall.

Escalera's passing residents of the living facility in the hallway -- including one in a mobility scooter -- before he's finally shot multiple times. First aid was rendered at the scene, but Escalera died.

A joint press release from the Kane County State’s Attorney’s Office, the Illinois State Police and the St. Charles Police Department, says Escalera was initially on the property to cut down a tree when he went into the lobby and started harassing residents with the chainsaw.

An autopsy revealed Escalera had traces of amphetamines, methamphetamines, and olanzapine -- a medication used to treat schizophrenia -- in his blood at the time of his death.