Yeah, I had the same thought.
Sometimes we wondered the same thing as well, which can completely and utterly suck. Not knowing where contact is coming from.
When bullets ricochet 5 inches in front of your friends face you wouldn't be questioning that. When you walk up to an objective that you where just engaging to find various brain matter, feet, legs, arms, hands, rings, watches, pants, shoes, rifles, RPG's, ammo, fertilizer, batteries, mines, mortar rounds, drugs, etc. all covered in blood, you wouldn't wonder. Of course, when you see somone with an AK with the muzzle flashing, you don't wonder. When you stand in a battalion memorial formation to remember the fallen, well, you definitely don't wonder. When mortar rounds start falling around you, you wouldn't wonder either, hah. I'm not saying you are questioning whether enemy was there or not, just being defensive I guess
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And thank you for the thanks lurch =D.
There are videos and pictures for public consumption (ie: this one), and then our own personal ones that would get us in a lot of shit if they ended up on the internet.