From a report released yesterday:
We recommend that New York (and other states) impose criminal liability for the creation by the perpetrator, or someone acting in concert with the perpetrator, of images or videos of a homicide. Such videos are an extension of the original criminal act and serve to incite or solicit additional criminal acts. In addition, these videos are obscene on their face. Importantly, appropriate legislation should avoid covering videos created by bystanders or passively, such as those captured by police officers' body-worn cameras.
It's certainly a crime to commit homicide (assuming the proposal would be limited to criminal homicide, and not to self-defense and the like), and to conspire with others to commit homicide. (Even if the only "acting in concert" is recording the images, that may well be viewed as purposeful aiding and abetting the killing, much as yelling words of encouragement during a crime can so qualify.) It's not clear whether the First Amendment would allow the law to tack on extra punishment for photographing or videorecording the homicide. But certainly there are ample tools to punish such people for the homicide itself.