How do you beat the last challenge with the boss fight? I see you can get m4 for more than one character but dont know how to get there.

Hello, I've tried and even made a custom level to try and gain "Safe distance". I've tried using assault rifle with at least guys 1 and 3, but it doesn't seem to work. In the custom level I've shot zombies from as far as possible but no luck. Another achievement that does not seem to be working at the moment is "Challenge accepted". Tonight, I beat all challenge levels and got a time / score for them but the achievement didn't unlock. I've also beaten all campaign levels, though 2-1 through 2-4 have not r...

I'm really sorry it didn't work out :( I wish I could help

游戏做的非常的不错， 值得入手