Am i a bad mother?? please read and help me!!?

i was walking my 5year old daughter (with ADHD) home from school today and she chucked her school bag in front of a car it had to swerve to miss hitting it. my immediate reaction was to raise my voice and i shouted at her to explain why what she had done was naughty. and said that when we returned home she would be going to her room. then all of a sudden i heard a male voice aggressively shout "leave her a fu*****g lone . i looked there was no sign of anyone there. now im a single parent i love my daughter dearly surely you have to teach thm whats right and wrong i wouldnt hit her ever but now im scared to go out as i dont know who shouted at me and also people have previously made anonymous complaints to social work about me.which were laughed out of court what if it happens again or i get hassle i have to walk past that road upto 4 times a day!!! was i wrong in my behaviourr telling her off and my reaction please help me. am i a bad parent??