If we can, let's put this death into the form of a something like a "Dead Schroedinger's Cat" and put it in a box for the time being.
You don't know for sure why this dead cat is dead, because you don't know enough about it, so you, being no sort of authority on the hidden and ever-changing features of the sub rosa, cannot make well-founded claims as to the causes behind this guy's death.
The "cat" is either dead from a legitimate overdose, or the "cat" is dead from being administered a bad cocktail by some agent of the empire. Unless you open the box, you don't know which it was.
The thing is, it's a dead fucking cat. And either way you look at it, drugs were involved. Does it matter if the guy was chasing his personal dragon and fucked up, or whether somebody showed up at his place and interrogated and killed him with his own drugs and some stuff found in the medicine cabinet? Allow me to carry the "penetration" analogy that some others in comments have mentioned, that in either case, the vector of "attack" is the drugs, the "attacker" being death.
Why would you want to fuck around with things like heroin or cocaine? I'm not a total drug-prude or something. I once spent an entire year, sans three days, high on some weed from Afghanistan. My cousin owns a successful pot shop in Colorado, and he's digging the new legalization just as much as I am. Of course, I can't smoke right now because it ruins my concentration and I'm going through college (a little late I might add) but that's all cool, smoke away, nobody ever died of a fucking pot overdose. I once did a couple doses of crystal MDMA, it was nice (nothing like what ravers describe Ecstacy to be), I felt super relaxed for the first time in my life since, like, adolescence, and it has had a nice, long-term residual effect, so that I don't think I will need to add to it for quite a number of years. But I would never contribute to my death with something known to be instantly lethal like cocaine or heroin. So many friends of mine have died using heroin, it's sort of a lost cause to tell me that there's A World Where heroin is okay to use. Cocaine is notoriously addictive and life-ruining, not to mention associated with heart disease (though some say it's a good agent against cholesterol levels). I tended to my Grandfather on his deathbed while I observed his decline accelerating due to his prescribed addiction to Xanax. So that's me, that's where I'm coming from.
I say it's stupid to do hard or addictive drugs. Look at what you're setting yourself up for: addiction and potential death. Where's the trade-off? "An altered state of mind"? There are plenty of safe hallucinogens to use. "Oh, I do it for the energy" that's bullshit, since I quite using caffeine and smoking cigarettes I have more energy than I ever did before. This is a documented side-effect of quitting systemically harmful drugs, especially stimulants. You don't have to worship L Ron Hubbard to know that some substances are plainly fucking stupid on their face.
And now look at the other possible quantum state of Dead Schroedinger's Cat, here. Suppose he DID get nipped by some secret agent spy-man. What was the cover-up? The guy's drug usage which some here believe is a made-up story but others have pointed out was a fact the guy himself made known. What would we be looking at if there wasn't this handy cover-up available, and a handy stash of drugs and well-stsocked medicine cabinet nearby to aid the implement of destruction? In all likelihood there would be a much more questionable medical examiner's report. So, again, the drug use serves up more "cons" than pros, this time directly to the people who are concerned with this guy's life -- fans, or whatever. You weren't getting high from this guy's drug use. There's no benefit to his drug use at all to you, but now that you're scratching your head wondering "WTF", there's definitely a major drawback to it, wouldn't you say?
So whether the dead cat inside is dead of its own cause, or somebody intervened to hasten death, it's a dead, drug-riddled corpse of a cat. The drugs present aren't doing anything for you, or for me, or obviously for the cat.
I'm not arguing for drug prohibition. I don't personally care which way drug laws swing as regards heroin and cocaine, because I'm never going to use them. All my friends who used heroin, guess what: they all DIED. No, I wasn't close tight friends with Huncke the Junkie, so I don't know about this one case where some dude lived to be old and decrepit while using heroin every day. All my friends who used cocaine are still using it, and it controls their lives even if they don't see it that way.
So, if this dead guy is some great big deal to you and you feel like you've really lost something here, then why don't you grieve his use of "hard" drugs?