According to numerous reports (I'm linking to the story on 1500 ESPN Twin Cities) Derek Boogaard's death has been ruled an accidental mixture of alcohol and oxycodone.
Oxycodone is in a group of drugs called narcotic pain relievers. It is similar to morphine.
Oxycodone is used to treat moderate to severe pain. The extended-release form of this medication is for around-the-clock treatment of pain. It is not for treating pain just after a surgery unless you were already taking oxycodone before the surgery.
From Hockey Wilderness, the SBNation home of the Wild:
This is sad, and yet somehow, welcome news. It brings another sense of closure to fans, friends, and hopefully, family. His death being ruled an accident means that it was not considered suicide, and that it is not tied, at least directly, to the concussions he suffered.
I really couldn't put it any better than that, so I didn't try. Rest In Peace Derek.