[Lemon:] And new information into CNN. This is coming from CNN's Fran Townsend, our security expert, who is saying that a lid to a pressure cooker much like this one, a six-liter pressure cooker, two of them believed to be what caused that blast. Fashioned with ball bearings and nails inside. But the lid to a pressure cooker found right across the street from the finish line of the Boston Marathon. And this will be used to help figure out exactly who may be behind this. So, again, a lid to a pressure cooker, six-liter pressure cooker much like this one, found across the street from the finish line there at the Boston Marathon, and, again, that's what investigators are going to use to try to put together, piece together exactly what happened. And in the wake of all of this, of this terror attack on Monday in Boston, you know, it has gotten people really nervous around the country. Understandable that many people across the country are anxious and they are attending large events like baseball games and NASCAR races this weekend. I want to go to CNN's Miguel Marquez. He is standing by now to tell us about how they're going to keep crowds secure for other events Miguel.
[Miguel Marquez, Cnn Correspondent:] Well, it's going to be very difficult there, Don. But it's not only people across the U.S. but around the world are watching Boston, hoping to learn lessons.
[Marquez:] When it comes to security at big events, despite the number of people attending, each event presents a different security challenge or nightmare.
[Tom Fuentes, Former Fbi Assistant Director:] If you have something like the Super Bowl football game or World Cup soccer, you have the majority of the crowd confined in a stadium of some sort.
[Marquez:] Places like Dodger Stadium, easier to protect. Vigilance and security increased since Boston. More thorough bag checks, more police presence. But in public venues, mass crowds not separated by stadium walls, security headaches multiplied. [On Camera] Organizers for this weekend's London Marathon are reassessing security plans for its 35,000 runners and tens of thousands of fans lining the route. It's the same problem in Tempe, Arizona, at this weekend's Pat Tillman Run. It's extremely challenging because it's not a secure environment. You know, we can't put fences around it. We can't put an officer every two feet. So we really on every set of eyes out there.
[Marquez:] With so many radicalized groups, or individuals out there, so many large events and soft targets, regardless of the event, the best security is knowing of the threat before the events occur. That means intelligence and lots of cameras, electronic surveillance and more law enforcement.
[Fuentes:] I think for the most part, the public has pretty much sad since 911. We'll live with that. We'll go ahead and accept that that's that's the new world we live in.
[Marquez:] Identifying who carried out the Boston bombing and will help security officials everywhere, but no where will it change the threat to large public events. Now look, Russian officials have also said in Sochi for the winter Olympics, they are watching what happens in Boston. And right now it's music, concert season, so you have Coachella Festival out here. They have a higher vigilance out in the desert here because of Boston and Fourth of July events. They're all swinging it because those are very open events as well. All all authorities looking at Boston, hoping that once they figured out what happened in Boston, it will helm them go forward and make their venues more secured as well Don.
[Lemon:] All right. CNN's Miguel Marquez. Miguel, thank you. It's certainly the season now, it's starting to warm up. More outdoor events, more concerts, more ball games. And again, I just want to give our viewers the information on the breaking news here at CNN. Our security experts security analyst, Fran Townsend, getting the information this morning that right across the street from the finish line to the Boston Marathon, a pressure cooker top was found on the roof of a building. Again two pressure cookers they believe investigators believe that what caused these two particular explosions here. They believe that the bombmaker fashioned the pressure cooker into a bomb by using nails and ball bearings and other explosive material. More information on the breaking news and other stories when we come right back here on CNN.