Sort:  

Ultimately, he died of a drug overdose. However, during his preparation to portray The Joker he had gone 100% in his efforts to think like a mentally unstable person with no scruples or remorse. That role changed his life; then it ended.

Oh my god I didn’t know this ☹️ He was doing all of these for a role! How extreme 😩

The drug overdose wasn't part of his acting preparation, but in his case it didn't help him when the drug overdose took place. His death was so sudden and unexpected that it was in the news for a few weeks.

Oh I thought it was anyways, taking drugs is very dangerous more than smoking cigarettes because I have seen my father being healthy and still smoking. But drugs are very extreme!