multiplayer collision problem

hello i am creating an online multiplayer game using HLAPI, i currently have a problem with my players collision. when 2 players hit each other or a player shoots at another player, the player that gets hit starts bugging : player rotation messed up (no longer faces forward when walking straight), physics not working...

i think it is due to the servers not syncing the players movement to all players.
i think that when i hit a player 2 on screen 1 with player 1, the information of player 1 hitting player 2 doesn't transfer to player 2's screen, so it snaps back to its place and starts bugging.

anyone know what is going on? and what i should do transfer from client to server than other clients?

thank you in advance for your help