Dawn
Thank you for your question and welcome to ADHDCentral.com.
Your story reminds me of when my son was around that age. He was home from school sick one day (my husband and I were at work) and he decided to "make" a fireplace. He used a large kitchen pot and made a fire inside it - in the middle of the living room! Luckily, nothing happened but it was certainly worrisome.
Certainly, your son needs to have consequences for his action. Consequences are best if they are immediate so he can relate those to the action. Long, drawn out groundings do not work as by the time the grounding is over, they may forget why they were being punished to begin with. The consequence should make him think about his actions.
ADHD - ADHD Symptoms: Impulsiveness
ADHD - Feeling Impulsive? Read this First
Cognitive Behavioral Therapy For Adhd
I hope this helps
Eileen
In the long term, helping him learn strategies to deal with impulsiveness is important. Cognitive behavioral therapy has been found to be helpful for some people.
I am also giving you some links to information you may find helpful: