Having watched the numerous videos online, it does appear to be a very low entry height and slow pitch rate, with an accelerated pitch response later in the loop, along with very low airspeed.
'IF ' this proves to be pilot error and a loop was continued when it should have been thrown away, then this pilot should face charges for the innocent loss of life as a result of his actions.
We all love aircraft and aviation, but you have to act responsibly anytime you are in control of something so potentially lethal, especially at a public event.
It is such a sad loss of innocent life.