Movie with Same Ending as American Sniper? (Warning: SPOILER)?

Hello,

I just watched American Sniper, and the ending was very familiar. In the end, where Chris is about to help the veteran, and the veteran gets a 5-second cam appearance where Chris s wife is looking suspiciously at him, and the veteran is looking like he is about to do something insane. Seconds after, the movie lets us know that the veteran murdered Chris.

I remember there is another movie (probably based on a true story also) that ends like this, where the murderer in the end gets a couple of seconds of cam appearance, where-after the movie ends by letting us know that the main character was murdered...

I hope someone can help me remember the movie I m thinking of.

Thanks! :)