Autistic children often have violent temper tantrums caused by a multiplicity of triggers. There is something in his environment or recent experience that has caused him to be stressed. Perhaps it was a story he heard on TV or something disturbing on the news (such as a home invasion) or a ghost story of something else that has put fears into his mind.
In any event he feels that he is not in control of the situation and may not know how to ask for help since he is so small. He may also be very frustrated that others don’t immediately understand his concerns.
There may be things in the environment (pictures, paintings, statues, toys) that frighten him. It may be certain noises or odors as well. These types of stimuli, innocuous to others, can cause aggressive autism behaviors if he becomes agitated by them.
He is become extremely anxious to the point of having panic attacks, which are causing the rapid heartbeats, in all likelihood.
Sometimes reading a story before bedtime will help. Often, an autistic child who is hungry will bet irritable and manifest this kind of negative behavior. Giving him a snack of his choice may very well calm him down.
Never give him any caffeine or diet drinks or snacks with MSG. Get an MSG –free snack.
Sometimes simplifying his environment can help. Make it easier to get around rooms, keep surfaces clear, put smiley face pictures up, and make sure that his toothbrush is not too hard (strange as it sounds, this can provoke anxiety and negative behavior).
Giving him honey sweetened chamomile or catnip tea will help as well.
You are certainly very patient and must continue to be.
If you have a doctor that you can see sooner, and if these techniques I discussed to not help, then you can ask the doctor if he can recommend some mild medicine to help at bedtime.
Unfortunately, this behavior is part of autism. He is fortunate to have a loving and patient parent.
I wish you continued perseverance and shall keep you in my prayers.
Elliott, MAE, LPCC, NCC, CCMHC