As of late Monday evening, there had been no suspects named. One 20-year-old Saudi man was detained at a Boston hospital for questioning though.
View slideshow: Mystery man on the roof near Boston Marathon bombings
The photo was taken by spectator Dan Lampariello, and it showed the second explosion at the Boston Marathon. Twitter soon went mad as the pictures started making the internet rounds. R&B singer Frank Ocean was one of the first to tweet about it.
"Who's that guy on the roof? #BostonMarathon #PrayforBoston"
Shortly after, the image had been retweeted more than 2,000 times and even more theories started coming out. The Daily Mail even questioned it on Twitter too.
"Who is this person? Individual seen walking on roof directly overhead as bomb goes off at Boston Marathon"
People on Twitter started asking "Who's the guy on the roof?" Others began questioning things too and one even noticed that "he's not reacting to the detonation."
This image went viral as Boston police and other law enforcement officials began pleading and asking for anyone that had cellphone videos or photos near the finish line to submit their footage to the FBI. The law is checking out any leads and information they can get in the ongoing terrorism investigation.