How doesn't VAC work in KF2??

I playing in a server, then 2 players joins, they are all sharpshooters.

And they use the same name :

IB1_UnTrusted930073 (ID: 76561198191727994, this guy has one VAC ban record)
lB1_UnTrusted930073 (ID: 76561198008291698 , his clone)

After one wave after, they both holding railgun and not shooting just aiming zed, but their kill counts keep increasing.

Also I see his clone "lB1_UnTrusted930073" just follow the "IB1_UnTrusted930073" and stop intermittently and keep aiming zed, just like a robot.

They both ended up 600+ kills in that game, a sharpshooter can kill that many?
Also....they kill the boss from within 10 second!!

We tried to vote-kick, but it didn't work because the votes aren't enough to trigger kick.

He even said : "Try to improve your skill lol", "I will tool-assisted your mom". and keep laughing at us because he won't be punished.

We taste a boring fight because they killed everything.



How does VAC won't auto-kick cheater in KF2??

My name : рокегмап (• _•) (ID: 76561197983573936)

How doesn't VAC work in KF2??