OMG Guns Everywhere

[Coffee Jesus]

Here's some research into how our racial biases can lead to false positives in weapon identification and assailant identification, especially when we're pressured to react quickly.

http://www.ncbi.nlm.nih.gov/pubmed/12500813

http://www.ncbi.nlm.nih.gov/pubmed/11519925

edit
In the context of "jumping the gun", I think it's noteworthy that you can flee from a knife, but not necessarily a gun. The defensive response to a gun is indistinguishable from the offensive response: grab the gun before they can shoot you. The gun owner will fear that they're actually taking the offensive course of action, ready to use his gun against him.