DS3 is a very bright and loving little boy, who is generally very well behaved and polite. He doesn't cope well with being hungry or tired and when he is either (or heaven forbid both!) he becomes very stroppy. He makes all sort of threats if we don't give in to his tantrums. (which we don't).
As an example: Tonight he is a bit tired as he had a late(ish) night on sunday, (we had a chilled out teacher training day yesterday) while reading with Daddy at bedtime he started to get silly. DH warned him that if he didn't read sensibly then reading time was over. He carried on being silly so DH followed through and put the book away. DS got cross and started saying he wasn't going to bed etc. DH said good night then put him in to bed and walked away. DS then stood at the top of the stairs threatening things like "I'm going to find my hardest toys and throw them at you" "Daddy you're an idiot" and "I'm going to burn down the house with everyone in it except me and Mummy"
After a while he calmed down and got into bed and was crying for me. I left him a short while then went and saw him - I explained that he had made daddy sad and that the things he said to daddy were unkind. He sobbed and said that he knew it wasn't nice and he wanted to say sorry to daddy. I gave him a quick hug and told him to go to sleep.
My older boys are quite a lot older and I can't remember if they did this, DH is worried he's going to grow up into a psychopath, I think he's just testing boundaries and trying to assert his control. Please tell me I'm not the only parent to a five year old threatening arson!