He might have an IEP/MDT report for all I know. He certainly had special attention to the school.
I disagree with your reasoning because your premise appears to be that if AL had been diagnosed with AS the investigators would have their answers and wouldn't have to look any further for an explanation.
This is not valid imo because a diagnosis of AS does not explain mass murder. The majority of people diagnosed with AS never murder anyone. Asperger would be a factor in why AL was so isolated but ultimately it does not answer the question why he murdered 27 people. Whether AL was diagnosed with AS or not some other explanations, causes, triggers and factors are needed to get a full picture.
No, my premise is that if AL had been properly diagnosed years ago instead of being shuttled about to various schools and then home schooled, this disaster may have been averted. The guy was seriously mentally ill and it didn't just happen overnight.
JMO