Grandmother Shoots Robber in the Middle of Taylor Swift 'Eras' Movie

Forget anti-heroes ... a grandma in New Mexico is a full-blown hero after shooting an intruder who was on the run from cops -- right in the middle of Taylor Swift's "Eras" flick!

Anissa Tinnin was watching the movie version of Taylor's tour with her granddaughter. They were having a great time, singing, dancing, popping M&M's ... when a guy named Joseph Rivera came charging through her front door. Turns out Rivera had allegedly stolen a car and cops were on to him.

Tinnin says she was manhandled, threatened and ordered to turn over her car keys, which she did. She says, "I told him not to hurt us ... I would do whatever he wanted."

She says when Rivera walked outside, she called 911 and beelined it for her gun case, where she removed a weapon.

For some reason, Rivera came back inside the house. By this time she had put her granddaughter in a bedroom for safety, but the guy came charging at her.

She screamed, "Get back. I will f***ing shoot you! " ... and she did. He asked why she did it, and Tinnin responded, "Because you're in my f***ing house!"

Tinnin even showed compassion, rendering first aid by putting pressure on the wound.

But, she warned Rivera ... one false move and she'd shoot again.

Cops showed up and Rivera is now in custody, charged with burglary, auto theft and other crimes.