Runners with head cameras. Spectators taking pictures. Surveillance videos from business. Police are searching through them all, and asking anyone who may have some to help.
"They had said that at the airport, there might be security slowed because they were saying to people, 'did you take any pictures at the marathon? Do you have anything?'" said Boston Marathon runner Janet Comi of Erie.
Asking the public for their videos and photographs, Edinboro University media professor Jim Wertz said, is a relatively new idea.
"If you think about the passage of time, there was a point where there was no camera available or one camera, that police would try to look for. Now, there's an abundance."
Wertz said it's a good thing so many people took pictures and videos, because now there are programs that can create 360-degree images from still pictures.
"I keep thinking about how technology can be incorporated into these types of events. I would imagine that kind of technology is being put to use right now."
And with that technology, Wertz said he believes whoever did this, was caught on tape.
"Whoever did this is on camera somewhere, and that's what the police are looking for at this moment. And I think these individuals have a profile of somebody by now that they're looking for and someone will stand out."
At this time law enforcement officials have not identified any suspects, or made any arrests.
Stick with the stations of Lilly Broadcasting for continuing coverage on this developing story.