another player can shoot me i multiplayer

Probably a mod or hack. That's definitely not supposed to be possible in the base game.

PC? They probably used the console changeteam command.  It happens occasionally, though extremely rarely in my experience.

Did you mean to attach a pic?  I mention since you said something about "red box".  Anyway, FYI, naming and shaming isn't allowed here, so if you do show, I'd suggest you block their name.

Ther was a red square around the player and the only thing the person wanted to do was sabotge for the others. If i got shot by that "player" i died

Hey, folks

This was flagged for cheating discussion. Although no specific player was called out, we are locking this to prevent name and shame from being reported.

This should not happen and it was sent up, but it sounds more like players modified things they should not have.

If you come across this again, or any other player you feel is breaking the rules, please report them as per the Hopw to Report Cheating article!

Cheers!