This is a good video to watch, the occult stuff was just the icing on the evil cake. The contrast between clips of how other performers stopped their shows while this guy amped it up as people were dying and an ambulance struggled through the crowd, is damning.
The details she gave in this video lend credence to the idea that this event was a pre-planned Satanic ritual. By itself, some of the suggestive imagery and language in the advertising could mean anything. But think about some of the details this woman gives: in the lead-up to the performance, for a gig that is explicitly aimed at families and children as well as typical fans of this kind of music, when people are supposed to be standing around in the sun, relaxing and getting into a party mode, they have 7 hours of ear-splitting, painful, repetitive electronic music, played at a loud volume, of the kind that people usually only enjoy when they are dancing frenetically in a dark dance club at midnight (perhaps on drugs), which points everyone on edge and into a bad mood, subliminally provokes arguments over nothing, etc.
Then the entire security team are EXPLICITLY told IN ADVANCE of the gig, "no matter what happens, don't stop, the show must go on," as if they're expecting something to happen which would normally result in the performance ending (as per the other performers - who all seemed admirably concerned to prioritize their audience's safety over the show continuing). The venue is too small for everyone present, people get crushed, the logistical arrangements are inadequate. Then, when people start being injured and dying, and the performer seems to know that this happening, rather than telling everyone to calm down (cf. the other performers) he tells them to go wild and crazy (presumably increasing the crush and making it harder for anyone to get some breathing space), insists the show has to go on, and looks into the crowd, speaking/singing in a sinister, deep tone, and seeming to enjoy the spectacle of chaos and violence, speaking.
By itself, any one of these points (even the guy insisting that the show must go on - some people are just irresponsible / self-absorbed) could be a coincidence, but together they give serious reason to think that he's knowingly involved in some dark things.
This is one of the most disturbing things I've seen in a while - even in clown world.