Where in the book does it say Seneca crane was killed hunger games?

Seneca Crane is not killed in the Hunger Games book. He is executed by President Snow for his actions in the 74th Hunger Games, specifically for allowing the two victors (Katniss Everdeen and Peeta Mellark) to survive.

The execution is described in *Catching Fire*, the second book in the series, towards the end of the book.