Aggressive meldown

Hi I’m new here and I’m just needing some advice my child recently had a meltdown at a community event ,shouted at people and when I tried to reassure her she thumped kicked and slapped me it took two men to get her away from me and unfortunately she slipped and they held her down. I asked them to let her go and gently soothed her. She lay on the floor kicking her legs and holding her head. I was concerned as folk were just staring at her. I asked folk to give her a bit of privacy but some stood with their coffee observing the spectacle. How do I deal with this outburst. My child is adult and hasn’t been officially diagnosed as yet but is on the pathway. 
please help