There will obviously need to be a big investigation, but watching it live it felt like it was coming. A full water bottle whizzed past Tommy Doyle's head as he was trying to take a corner and at least another 4 missiles landed at the same time. According to some reports a home supporter pulled a machete from his coat, and we had the pretty shocking scenes of players having to go into the crowd to rescue their children. I suspect that is why there were so many substitutions as the game restarted, players like Kyle Bartley weren't willing or able to carry on as they wouldn't leave their families.
From the footage that was shown it looked like both sets of supporters were involved, so the FA are going to have to come down hard, and I suppose the ultimate sanction would be to expel both teams from the competition.
All credit should go to Thomas Bramhall and his team. A relatively inexperienced referee but he appeared to handle the situation perfectly and had a very good game.