Once you are out of harm’s way, look again for any help you can offer. If you have intelligence from anything you observed, find law enforcement and report it as fully as you can. If there is none, stay out of the way of emergency personnel; do not gawk; and leave the area, as another attack could be unfolding.

If you have become separated from your group, send a text message. Do the same with a family member or friend elsewhere so your loved ones do not worry needlessly about you.

Should you rush a gunman? If you are militarily or otherwise trained, you might look for such an opening. We have an example of that in August 2015 when three Americans—including two servicemen—stopped an attack on a French train by rushing the gunman. But generally speaking, that is a last resort.

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