There's a great song on the subject.

What did they do to Tupac?

The police report says both that he pulled the trigger with his shoe laces and also that he was wearing his shoes that were tied. The amount of heroin he took would have knocked out the biggest user within seconds, not really giving him time to act afterward. And then there's the fact the house was unoccupied for over two weeks and out of the blue had a technician come over to fix something the day after he died so they could find the body.

Then there's the suicide note. The first 2/3rds are somewhat positive, then the latter portion gets dark and the handwriting completely changes.

I don't know that Courtney did it, but Kurt did not kill himself