Haven't seen it but Rotten Tomatoes was brutal with a 11% rating
https://www.rottentomatoes.com/m/man_down/IMdB score is 5.9 our of 10.
http://www.imdb.com/title/tt2461520/From the description, it doesn't seem to line up with the preview of a Marine dealing with PTSD.... so I'm kinda confused.
"In a post-apocalyptic America, former U.S. Marine Gabriel Drummer searches desperately for the whereabouts of his son, accompanied by his best friend and a survivor."