Glitch base

I was playing on "Freezzer #SANDBOX #1-5 and i came across a group of three making a glitch base inside St.Petersburg tunnels,it looked like they were attempting to do the Mk2 achievment. since they were trying to shoot us through the tunnel walls and couldn't kill us they resorted to using a rocket launcher and did kill me a few times. A lot of people were trying to attack them but couldnt because they kept lobbing rockets through the walls. (Evidence and suspect names: https://www.youtube.com/watch?v=M-SyC8qclEg&edit=vd)