I would like to look at it in a slightly different light if you would let me. Who would set any thing on fire on purpose just because they are angry? May I use a different word.., more closer to the heart of the offender, it could possibly be an 'unbearable emotional pain'. Something far beyond just anger and the manifestation of it in setting something or someone on fire, which is the problem to be dealt with. If you or someone else wants to set things on fire, I do not think reporting to the authorities would be a long term solution, while it might be a safety measure, according to the situation. The question lies in whether you are concerned about the persons' health or what the person does as a result of his ill health?? Which is it? Much Love and God be with You. The Friend.