FDA raised the age from 18 to 24 for monitoring the start, or midificaton of dosage, of Anti-Depressants, a few weeks after the Virginia Tech Shootings. I have never read what the drugs were he was taking. I have read accounts from his roomates that Cho would take pills in the morning, when he used the shared bathroom.
I have not read anything about the Autopsy.
If Autism was a factor, Anti-Depressants are contra-indicted by some sources.