There are some forms of epilepsy that include temporary psychosis or hallucinations. Vomiting is also common.
Handcuffs may or may not have been called for, but how they handled him after the vomiting began is critical since choking or aspiration of vomit can have fatal consequences.
Autistic and epileptic. What a double whammy.
Very sad.
Threatening to kill his own family would seem to warrant handcuffs.