Was Walter responsible for this character's death in The Big Lebowski?

Watching The Big Lebowski (1998) again, for the Nth time, I felt a bit silly.

Pretty much everything that the Dude brings Walter in on gets screwed up. Yes, throwing either ringer would have resulted in the same thing, but that's what started his car getting wrecked... and shot... etc.

In one sense, if the Dude and Walter hadn't done things the way they did, they never would have found out the truth in the end. However, it was Walter's interventions/plans/decisions that ended up putting the nihilists in that parking lot with Donny, causing the situation that brought on his heart attack.

So... did Walter kill Donny? Even inadvertently...

Not really. First of all, just about everyone involved brought about this complex situation. Everyone's (usually misguided) choices - Bunny, the Dude, the big Lebowski and the nihilists themselves - put the nihilists in that parking lot, so everyone would be responsible for Donny's death. And we don't even know Donny's prior health condition. In short, you can't put the blame on just one person.

Plus, it seems that Donny was destined to have that heart attack anyway because this is foreshadowed: Just before they go out to the parking lot, Donny misses a pin (for the first time in the movie, if I'm not mistaken). As he goes back to his seat, he seems off; he winces and feels his arm. Pain, weakness or numbness in your arm is one of the symptoms of a heart attack. [Look for 'foreshadowing' here.]