****Spoilers!!!****
I would say that Chloe got in and redirected the video feed, the explosion if you look closely is highly digitized, you see a whole bunch of green grass squares going up, so if it's not that it's just very poor graphics on their part. Sounds far fetched, because she would have to find or create video footage and feed it back to them, seems impossible, but it's tv after all. The experts say that whenever a notable character died the clock ticking in the end would be silent, and here it wasn't, so that's another clue that Heller isn't dead, yet.