Heres an up-close look at the guy (sorry its a bit crazed-up, it was lagging a bit, and I wanted to get as close as possible before he got killed
And in response to Aaron:
1. They use a barrel of TNT, which acts like a super-powered siege charge. The only difference if they don't throw it, you need to be in close range for it to hurt you.
2. All they really did was just let you get close, and then blast you.
3. They can one-shot anybody, including myself and a level 50. So, stay away, mates.