The siege against humanity

You decide that the safer way to kill is to become a specialist, you walk over to a tent and meet your squadron, 2 other guys and 2 girls are looking at a wall with different weapons, you walk up and look at the wall up and down before settling on a sniper rifle, you are put into the back of a truck with the rest of your team and you wait for the fighting to start. The truck speeds down a trail through a thick forest when "KABOOM" you hear a loud explosion and the back of the truck sinks down a but, both of the back tires popped, with no extras you and your team have to keep walking on foot following the road. As your team keeps walking they realize that 3 mechs were following you the whole time, stalking, waiting, they were the reason the tires popped, the mechs don't realize you know they are there yet, but you all know that you need to do something about them, your team decides that you guys can either run into the forest and take cover, or turn around and give them everything you've got.