First thoughts?
He is probably not pretending he was hit by a car and there is probably not much his parents can do. To presume that they "don't care" reads as pretty ignorant to me. You have no way of knowing how much they do or do not care.
I suggest you educate yourself about autism. You could also approach the parents and ask if they need any kind of help, or just to simply offer a friendly hello. If the rest of the people in your neighborhood are as quick to judge as you are, the parents probably feel pretty isolated and alone. If you are genuinely concerned, it might help both them and you if you took the time to befriend them and educate yourself a little bit instead of passing judgment.
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Mom to 2 exceptional atypical kids
Long BAP lineage