There's gun control here in the USA as well. Maybe you can educate yourself regarding the German gun laws.
This (now dead) criminal could have had access to firearms including semi-automatic pistols, but the shi thead wasn't disciplined enough to go through with the required process, and he probably didn't have the scoots to buy one on the black market or wasn't plugged into the ISIS network.
I find your assertion that if a passenger was packing that there would be more dead dubious at best.