Anecdotal evidence, but then so was yours. Hell a lot of people used to carrying weapons tend to reach for them even when they don't have them on, I still sometimes do. A gun is a mental security blanket. Now, let me say more importantly that this is not proper debate, we do not use anecdotal evidence, we use science and reason when trying to press facts. If you want to assert people in a panic forget they have a gun, check. Run a study, either a very large one to grab a decent sized sample of concealed carry, or just do cops or soldiers. Bring them in ostensibly for something else, like their favorite soda or whatever, and in the middle of it with video running drop a flashbang in the room or hit the stereo on full volume or whatever and see what percentage reach for their gun. That would tell you what percentage of folks who carry weapons tend to react when startled by reaching for it. That won't tell you how many would react to a shooter, presumably more will reach for a gun during a 1-5 second period after their brain screams 'homicidal lunatic with gun' though I daresay the 'with gun' bit is even more likely to set off 'Gun! Gun! Oh, yeah, I've got a gun too'. Also, I think the weight of common sense is that once a person has a hand on their weapon they are very likely to begin including opening fire on their list of responses. Regardless, you can't just make assertions like that as fact, especially if disputed, these things need testing.