Hmm.
So I have only ever posted relating to the UK terrorist attacks earlier this year, but the circumstances of this caught my eye.
All I can say is from my own experience of the effects of delirium following overdose - though in my case very different: I have never touched any drugs recreationally, but took a massive dose of [a very common antihistamine which you can buy in any pharmacy here] in a serious attempt to end my life.
Now in my incident, I woke up 36 hours later in an Intensive Care Unit. This is my first thought here: Is there knowledge of whether this person was checked out medically after the incident? It would seem odd that someone could take enough of a cough syrup to induce hallucinations/delirium/loss of any control and police or paramedics not want that person checked over, even just from their own point of view to prevent potential harm in custody? From reading the effects of the drug he took, it has potential to be fatal, or at the very least to cause serious harm at very high levels.
I absolutely without a doubt know that you can have absolutely no control or awareness of what you do whilst experiencing delirium. The first thing I was told after I regained consciousness was not to be scared, but that I had a lot of bruises because the police officers who accompanied me to hospital had had to restrain me so hard (apparently because I did not treatment) because I was so combative, agitated and confused as a result of said medication - never in any trouble for this, because police said they absolutely knew that it was a result of being very very medically ill. I am not ever in any way aggressive, violent, it's about as far from 'me' as you could possibly get, but I am told I fought incredibly hard. So absolutely drugs can cause extreme behaviour.
In my experience, that behaviour, following medication-induced delirium, was still very very confused and 'unusual' behaviour. Whilst I have no memory whatsoever of it, I came home to find things like my duvet in the middle of the floor, a contact lens solution bottle on top of the fridge, things which I had quite clearly done but made no sense. Somehow the level of 'premeditation' or 'awareness' required to go and get something from its rightful place, return to the 'right' room, and do something seems higher. That said, we know people sleepwalk and do very 'normal' or 'routine' things with no awareness, so...? (Just, in my experience, medication-induced delirium is extremely different from anything close to sleepwalking or dreaming).
My final thought: Reactions afterwards? I don't know. I know when I regained consciousness, I couldn't have made any suggestion as to what had happened - the loss of control and loss of memory/awareness is such that it is literally a total blank. But for someone who says he had 'heard it was a good feeling/would help sleep', it is a remarkably 'controlled' reaction to coming to (if that makes sense?) Personally I was absolutely terrified at 'coming to' with a complete blank of a period of time (not knowing what time/day it is, what has happened, how you got to where you are, the realisation that you can do something whilst having absolutely no awareness or memory of it is...in itself extremely traumatic). I was distraught afterwards at even the thought that I was resistant enough for police to have to restrain me so hard as they did. The reaction in this case is unusual, to say the least. Though again, grief, trauma, confusion, shock, can do odd things to a person, so...
This is just my experience (and of a different drug, which I appreciate may be completely different). But medication-induced delirium/hallucination/loss of awareness is not something most will experience, so I hope it is useful to understand a little about what it can actually feel like...and how people may or may not react to it...
[Oops, apologies for essay!]