That plane was N557PG, a Cessna Citation V which is, according to the FAA, registered to National Aircraft Leasing Corp. That company is probably a front company for the FBI. Here's the track that N557PG flew on June 2, 2020. Compare to the image in your question:
Here's a link to see that track yourself. Note that it is probably only good until July 2, 2020 (about 30 days after June 2): https://tar1090.adsbexchange.com/?icao=a71ab8&lat=38.785&lon=-77.308&zoom=10.2&showTrace=2020-06-02
All the commercial trackers, like Flightradar 24, will hide aircraft identification info if requested (and paid) to. ADS-B Exchange is probably the first place anyone should check if they want to know what's flying around, because it has good coverage (maybe not as good as the commercial trackers) and never censors any information. Use https://tar1090.adsbexchange.com/.
After the 2015 Baltimore protests over the suspicious death of Freddie Gray while in police custody, it was found that the FBI had been flying more than a hundred aircraft over U.S. cities as part of a secret aerial surveillance program, where those aircraft were registered to front companies to hide their relationship to the FBI ("FBI behind mysterious surveillance aircraft over US cities" by Associated Press). National Aircraft Leasing Corp. was one of those front companies. You can see from the FAA registration database that there are 7 other companies, all fronts, with aircraft registered to the same address:
We know the flights are at least collecting video (including thermal/IR) surveillance because the FBI released some of it:
(FBI archive link: https://vault.fbi.gov/protests-in-baltimore-maryland-2015/unedited-versions-of-video-surveillance-footage/1D3001Part1
). We know they have the equipment to do other sorts of surveillance too.