Holding a camera and recording video while in no direct danger does not make someone a hero.
If the video you are recording is a murder, and your video will have a direct impact upon the murder's ability to get away with the crime, it most certainly does make you a hero. If the cop had noticed, he could easily have made it two killings, "accidentally" smashed the phone, and got away with both. Afterwards, the videographer's got a murderer and an unknown amount of his buddies pissed off at him. And these are people skilled in investigation with the full power and resources of the state behind them. They WILL find out who he is and where he lives.
I had a relative who reported a cop for assault once. For her troubles, she got to suffer months of pointless traffic stops, parking tickets, and car vandalism. If a murder was involved...I don't know that I'd want to expose my family to what could happen.
This person was either amazingly brave or amazingly stupid.