This is audio from Boston PD immediately after the bombs went off - Delta 984 appears to either be a supervisor or at least the one in charge by virtue of location (I'm not sure how BPD's rank and identifier system works, it varies by department). The intention here isn't to second-guess anyone, just to get an idea of what went on during and after the attack. It's good to hear someone keeping things organized, dispatch working smoothly to coordinate and to see these men and women charging in to help despite knowing there might be secondaries (and that goes for fire, EMS, runners, bystanders - everyone that responded). If you listen as far as 8 to 10 minutes in you'll hear them start organizing help from additional responding agencies, tactical measures, use of social media to reach the public and other coordinating efforts.
The FBI is the lead agency for this investigation:
The video was uploaded by Firefighter Dispatch and shared by LawOfficer.com.