Begin with conduct you can describe.
Suspicious activity is not a look, a language, an opinion, or a person who is unfamiliar to you. It is behavior that, in context, may indicate preparation for a crime or violence. Note the place, the activity, its timing or repetition, and any normal explanation you can see. A public photograph may be innocent. Repeated attempts to enter a restricted room after being redirected deserve a report.
Questions to ask yourself.
- Is someone trying to get into a space they have no reason to enter?
- Has a person returned to test a boundary, door, or procedure after staff explained it?
- Did you hear a specific threat toward a person or place?
- Is there an unattended object alongside another credible indicator of danger? Leave it untouched and tell staff or police.
- Would an ordinary explanation fit what you saw? Tell the reporter what you know and what you do not know.
Act at the right level.
For immediate danger, move to safety and call 911. Otherwise, tell the responsible staff member or local law enforcement promptly. Do not follow, challenge, search, or investigate a person. Report actions and exact words. You do not need to prove intent for someone qualified to assess a concern.
Source: DHS guidance on suspicious behavior.