My friend was killed inside our base (near MB tisy) in a place he couldn't get shot from around 10:00am (central US time). He messaged me saying he thought it was a cheater. He had been online for 20 minutes or so and had confirmed that our walls were still in place and that no one could be inside. Hearing gunshots at Tisy he decided to sit still and listen inside our base for people approaching. He heard nothing before he died. Again, there was no angle he could've been shot from.
The walls of that base are thick and our constructed walls were still intact.
I logged in around 10:30am (central US time). Upon loading in I was shot from inside my own protected room almost immediately.
When I got back to the base boxes had been taken from inside locked rooms, some gates were only half destroyed but their locks were taken off - others fully destroyed, and things were generally done in a more destructive than necessary way. Players would usually take an easier way into the base, but these people took the path through the most walls and gates possible.