Latest news is that it was probably an overdose on sleeping pills - hopefully it was accidental.
There is no such thing as an “accidental” overdose on sleeping pills really. You need a massive overdose (think: 50 to 100) to kill yourselve.
That would depend on a lot of things, actually.
They could be extra super-strong pills, and he accidentally took as many as he would if they were regular ones. That’s doubtful, but a possibility.
He could have taken a whole handful of them, thinking that he really needed to get to sleep but would have a hard time doing it.
He could have had a lot of alcohol first, and then taken the pills. The alcohol would boost the potency of the pills, especially if he was really drunk and forgot how many pills he’d already taken.
Yup, he was on Stilnox. Apparently known as Ambien in the US. Has some side-effects (including sleep-walking) that’s caused the Australian Adverse Drug Reactions Advisory Committee to put the stuff under review.
The only really dangerous sleeping medication are the old fashioned barbiturates, which are no longer prescribed. Modern sleeping medication like Stilnox or Temazepam really is not able to kill you unless you take really, really massive quantities (or mix it with other, more dangerous medication like Ledger apparently did). And I really mean “massive” here, not a handful but 100 or more. The only effect of taking a large number of such sleeping medication is that you go into a really long sleep/coma for several days and then wake up again. Not that that is healthy to do, as you risk the possibility of brain damage of some sort too. Believe me: many would-be-suicidals have gone through this disillusion.
So, when things like this happen with sleeping medication, they are really not “accidents”. In fact, seeing the list of stuff that Ledger apparently took in combination and caused his death, I doubt whether that was an accident (or otherwise he had a seriously incompetent doctor). But then, I am not a doctor or coroner of course.