How does Henry Gatz hear about the funeral? no

Henry C. Gatz in The Great Gatsby sees that his son has died when he reads the Chicago newspaper.  After he arrives at the house in the novel, we read:

"I saw it in the Chicago newspaper," he said.  "It was all in the Chicago newspaper.  I started right away."

He is then at the house, for the most part, with Nick until the funeral, so he naturally learns about it. 

He shows great pride in his son's accomplishments, and disappointment when so few attend the funeral.  He also echoes the title of the novel when he says that his son would have been a great man if he had lived.