Against what?  Murder?  How do you stop someone from steering their car into a crowd?  How do you stop people from having a desire to kill?  How do you stop people from changing religions? How do you prevent some weak-willed, violent-prone kid from being talked into doing something stupid?
Over the years in the US, there have been over a hundred incidents of mass murder, claiming hundreds of lives.  I don't see you wailing and moaning over that.  Why does it only matter when the killer is Muslim?  Do you think Christian bullets can't hurt you?
Violence will happen.  Murders will happen. You can't prevent them without illegally taking away our democratic rights.