This is from a news story about a traffic accident.
It was driven by 44-year-old Catina Isaacs, who state police said died in the crash.
If you read this blog with any regularity, you might expect me to say that “who” should be “whom,” but the sentence is correct!
Look for the verb. We have two of them, “said” and “died.” Now look for the subjects. “Police said” is obvious. Now what’s the subject of “died”? It’s “who died”! Not “whom died.” So the nominative form of the personal pronoun is correct.
My condolences to the family.