Actor Bradley Cooper will always regret not meeting retired Navy Seal Chris Kyle in person after snapping up the movie rights to his book over the phone.

Kyle was killed on 2 February (13) when another soldier he was helping overcome post-traumatic stress allegedly shot him, and Cooper is upset he'll never get to meet the American military's deadliest sniper in person before portraying him on the big screen.

The Hangover star tells Details magazine, "I only talked to him on the phone. And I've since corresponded with his wife (Taya). The whole thing is just awful. I mean, (he left behind) two young kids."