They may have been on some type of anti-depressant. It would explain a lot.
When my father died suddenly while he was out of town, I had trouble sleeping the next night after both the shock and the need to make arrangements. A well meaning neighbor who was a registered nurse gave me something from her little at-home pharmacy. I had no idea what it would do to me. As I had had no sleep for a day and a half and had been unable to eat, it totally zonked me out. I regret I hardly remember anything from the wake.