You are correct of course but do you think all tools are equally dangerous?
There are too many variables to definitively conclude that a firearm -- ANY firearm -- is going to cause more casualties than using something else. Using the "all things being equal" approach doesn't address the individual involved, the skills they possess, and the planning they did prior. As you said, the gun is a tool. Not everyone is as skilled at using a given tool as the next guy.
Case in point: Bows don't make the noise firearms do. You could do a lot of damage with a bow from concealment before anyone knows what is happening. Any police or security guard response would be delayed, as would their ability to locate you. The crowd would also be less likely to panic, flee and take cover without the sound of a firearm alerting them to danger.
In a controlled environment, firearms are more accurate, have more range, and can be brought to bear more quickly than most weapons. But, that doesn't make firearms the most effective weapon in all circumstances. Playing COD should have taught you that!
