I got a question for you: Holly and Gerry are a married couple who live on the Lower East Side of Manhattan. They are deeply in love, but they fight occasionally. By winter that year, Gerry suddenly dies of a brain tumor, and Holly realizes how much he meant to her as well as how insignificant their arguments were.

Answer this question: how did gerry in ps i love you die?
Let's think first:
The important part for answering this question is: By winter that year, Gerry suddenly dies of a brain tumor, and Holly realizes how much he meant to her as well as how insignificant their arguments were.
Therefore, the answer is of a brain tumor.