The attacker, who asked people if they were Muslim before he stabbed them, was shot dead by an off-duty police officer from another jurisdiction.
There are reports that the attacker was wearing a private security firm uniform.
to stab - to pierce someone's skin, muscles, bone, etc. with a sharp object (knife) and wound them
off-duty - not working at their job at that moment
jurisdiction - an area of a city covered by police, lawyers, judges, etc.
private security firm - a company that provides safety officers that are not police officers
uniform - the (same) clothing worn by staff employees, police officers, military people, etc.