How is this games anti cheat so pathetic on official

Me and my spent like 15 hours on chenarus looting gas zones and our goal was to do a circle arround the map and we stopped at kamysho when we log in today we get instantly killed with a giant blood splatter and some melle hit sounds while completly hidden inside we respawn we run there only to get killed in the same way again while running through the forest and a bit later we spawned in a closeby town only to see a duo of 2 russian guys wearing 1 to 1 our gear and shooting our weapons with the same giant blood splatter each shot. How does one make such a shit anti cheat in an online game