My daughter is 8 years old. If you saw her in a photograph, you'd think "pretty girl, nice smile" - if you met her in person, I'm sure your perceptions would change.
You see, my daughter has autism or ASD - also known as the "invisible disability". The autistic spectrum is wide and varies from mild to moderate to severe difficulties.
Autism affects my daughter in many ways but the main three are: Speech & language difficulties Delayed social skills Obsessive compulsive disorder. She also has delayed motor skills and heightened sensory awareness.
Fortunately for me, my daughter is verbal but when her anxieties take over (which they do if she is faced with a change of routine/sensory skills overload/an unfamiliar situation), she will either bolt (run away fast without thought for her own or others safety) or meltdown (totally emotional and sometimes violent outburst).
I risk assess everything before we travel anywhere - even a trip to the supermarket has to be done at a quiet time and we use her special needs buggy as her comfort zone. Even then a person in the next aisle may look threatening to her or she will be startled by a sudden noise and she will want to leave immediately.
So, that child breaking down in public may not necessarily be "behaving badly" - look beyond your initial thoughts and at the wider picture.