Gun vs. no gun. In this case that's an interesting proposition that we will never know. And no one really wants to find out.
The banquet hall was hosting the 5th anniversary of Learning Together, that brings together criminal offenders with others involved in higher education:
[www.bbc.com]
So attending the conference were ex-criminals, corrections officers, banquet hall staff, and (I'll just call them) graduate students. If the attendees were only graduate students (there for a different purpose) the Polish national Lukasz would have had a harder time of it or maybe have been killed. The graduate students most likely would have just pooped their drawers and died. But the ex-criminals, and to some lesser extent the corrections officers, surely know shit when they see it. Add in some of the staff to fill in the gaps (and that is only because of the presence of a couple bad ass guys) and they have their defense. Gun or no gun the criminal knows when he is fucked and isn't going to be too happy about the situation. I think that it's safe to say that if Khan had a gun there would have been a higher death toll and Khan probably would have escaped (if he wanted to) only to be apprehended later. But because of the people that were present at the conference some immediate response to the attack was a certainty. Khan actually chose the wrong target.
GAK67, I don't know where you are from. But in the USA we have a 2nd amendment and we are keeping it. And all the whining around the world (and inside our comfy USA bubble for that matter) won't change that.
Oh I need to add that (Khan)gun or no gun, if someone attending had been armed with a gun Khan is dead on the spot.