The FBI released the surveillance video and pictures for the first time today.
The agency says they want to get as much help from the public as possible and they hope this helps spur others to come forward.
Peter DesLauriers is the agent in charge in Boston, he said "the nation is counting on those with information to come forward and provide it to us."
DesLauriers added. "No bit of information is too small."
DesLauriers said of the suspects "we consider them to be armed and extremely dangerous."
The FBI believes one or both of the men placed the backpacks near the finish line and then walked away.
Just seconds after the pictures and video were made public the FBI website crashed due to overloading.
See the video below and find more details here.