as we mentioned, hundreds of rioters have already been charged for their actions on january 6th. but one of the largest and most complex investigations in fbi history is ongoing, as investigators work to identify people who stormed the capitol. nbc news correspondent pete williams has an inside look at the fbi's work. >> a year after the worst attack on the u.s. capitol since the british torched it 200 years ago, the fbi hasn't stopped working to identify rioters. this exclusive look shows agents and analysts combing through tens of thousands of photos and videos. investigators also used facial recognition software and cell phone records that allowed them to plot the movements of individual people inside the capitol, the largest use ever of that technique. >> it was all over the capitol grounds. >> steven -- is a member in charge of the washington field office and says a priority now is identifying rioters who attacked police, like this man,