Multicopter pilot here. In short, it looks like the pilot was a hobbyist out of his depth and was performing dangerous maneuvers before any so-called hacking with equipment not meant for the job.
I don't know a lot about the specifics of the accident, but the multicopter that was involved in the accident was using a very outmoded form of technology to control the multicopter (wifi) rather than the far more reliable multichannel failsafe 2.4GHz DSMX systems that are in common use with bigger multicopters. While it may be possible to "hack" the signals controlling the 'copter, it's more likely that the control loss was due to RF interference, either by purpose or accident. I would imagine that a sporting event such as the one where the incident occurred would be awash in wifi signals from dozens if not hundreds of sources.
Secondly, the multicopter pilot was doing something that experienced pilots / cinematographers strongly avoid: flying directly over people. Even the best control systems and multicopters can malfunction, and hovering over a crowd is obviously a bad place for that to happen.
The type of multicopter also gives away the apparent lack of skills or experience of the pilot. Parrot AR 'copters are not professional-grade equipment and they are not devices that someone who earns a good bit of money from aerial filming would use.
(note: apologies for a double post, I forgot to log in to post this reply.)