We live in a world where you now need to assess your safety at public events and among crowds even beyond "See something, say something" situations.
The Department of Homeland Security says that if you see something suspicious taking place, then report that behavior or activity to local law enforcement or in the case of emergency call 9-1-1.
Factors such as race, ethnicity, national origin, or religious affiliation alone are not suspicious.
For that reason, the public should report only suspicious behavior and situations (e.g., an unattended backpack in a public place or someone trying to break into a restricted area) rather than beliefs, thoughts, ideas, expressions, associations, or speech unrelated to terrorism or other criminal activity.
It was a backpack left at the East 55th Street RTA rapid station Tuesday morning in Cleveland that led police to close the area after it was reported.
Related story: RTA police: No explosives found in suspicious back pack
We learned Tuesday that investigators believe the bombs at the Boston Marathon were shrapnel-studded pressure cookers, hidden in backpacks and set off by timers, law enforcement officials told NBC News on Tuesday.
Law enforcement officials told NBC News that the explosives were classified as low -- meaning that they traveled at under 3,300 feet per second. That is not enough to create a blast wave, which can kill people from air compression and blow out faraway windows, but it is enough to propel shrapnel a great distance.
So how do you take precautions in your everyday life so that you can protect yourself and your family at public events where something might happen?
Former U.S. Secret Service Agent Evy Pomparas on Tuesday's The Today Show gave some suggestions on how to go about your normal life with an eye to safety.
First, is the event inside or outside?
If outside, is there a mailbox or trash can nearby? That's the perfect place to hide something so avoid standing near them.
Stay away from large windows or glass walls, as an explosion or gunfire could turn them into dangerous shards of glass flying through the air.
Pomparas says to stay near walls of concrete or concrete and stell to afford yourself the most protection.
If you are inside, take notice of different exits. If there is an emergency, do not follow the main crowd out one exit but pick a different exit, so as not to be possibly crushed in a panicking crowd, Pomparas said.
And if you are trying to alert loved ones to the emergency, it is better to text rather than call on your cell phone. Texting takes up less band width and it's more likely the text will get through.
When you park your vehicle an event, don't always think about getting closest to the building or the outdoor venue. Think about positioning your vehicle for the quickest escape route, whether it would be over a grassy area, through a yard or down a side street.