Aurors
Harry was cooking when the news came, and after fire-messages to the Order, he barely had time to leave a note for Al before getting everyone together and taking off. He told his mum to stay out of sight from Aurors and stick with the Order.
They appeared just outside, and getting the heads of units together they split the tasks and got to work nearly immediately. Homicide, Major Crimes and Support inside to calm the crowd and catch as many Death Eaters as possible. Potions working on destroying the CCTV to make sure no magic was caught on camera. As soon as Bill and Severus arrived, they went to work with braking the curses on the doors to allow people to get out. Hopefully without too many injuries.
There was no way to cast anti-apparition jinxes on the place which was good in the way that it let them inside, but bad as they could not prevent the Death Eaters from escaping by using them.
All he could do was hope that they'd catch a few of them, and save as many lives as possible. Though as usual they weren't nearly enough people. 76 000 people inside, in full panic, and only 151 Aurors to handle them as well as arresting Death Eaters. Even with the help of Hit-wizards and the Order they weren't nearly as many as they needed to be.