Snorting cocaine in a nightclub is not how I would mourn a child, but different people do react differently to grief, so although I do find it weird and am not 100% convinced by his excuse I do think it could be the truth. So this was probably the right decision - at least, in the circumstances I do think no other decision should have been taken.
Though obviously he did know where to get the coke and how it would make him feel, so he'd most likely taken it before. Right decision, but I'd keep an eye on him tbh.