In a new essay for Time, Sorkin recalls his friend's now chilling words during a break from rehearsing Charlie Wilson's War, the 2007 drama starring Hoffman and written by Sorkin.
The two had bonded over their shared struggles: The West Wing creator abused cocaine in the '90s, and Hoffman battled heroin addiction throughout his life.
"I told him I felt lucky because I'm squeamish and can't handle needles. He told me to stay squeamish," Sorkin, 52, writes. "And he said this: 'If one of us dies of an overdose, probably 10 people who were about to won't.' He meant that our deaths would make news and maybe scare someone clean."
The conversation proved ominously prophetic. Hoffman was found dead of an apparent overdose in his West Village apartment Sunday morning. He was 46.
Since then, police have arrested four people in connection with drugs found in his apartment, and Desperate Housewives actor Shawn Pyfrom came forward with his own story of addiction, spurred by Hoffman's death.
But Sorkin wants to make clear that Hoffman – whom he calls "this kind, decent, magnificent, thunderous actor" – didn't die from an overdose. Heroin itself, he says, killed him.
"We should stop implying that if he'd just taken the proper amount then everything would be fine," Sorkin writes. "He didn't die because he was partying too hard or because he was depressed – he died because he was an addict on a day of the week with a y in it."
Later, Sorkin lists the Oscar winner's many awards, urging, "Let's add to that 10 people who were about to die who won't now."