Safety rules

What do you do when a child disregards safety rules being reinforced by the homeroom teacher, the teacher's aide, another volunteering adult in the room, and a peer, and the child still goes ahead and does the thing they were specifically told NOT to touch? (context: hot glue gun) 

I'm genuinely scared for this child's safety. FOUR times I've witnessed this child reaching for the hot glue gun to work on their art project after repeatedly being explained to them that they must consult an adult--I'm not sure if it's blatant disregard or just they don't understand either of the TWO languages the safety protocols for the class being spelled out.