I am so sorry for your loss. It is not quite the same, but when our dog passed, I found that it helped, our then three year old, to read/hear books/stories about the subject.
With that, you know if your family is taking a religious approach to the puppy dying; e.g. 'God's Will.
The books that I found most helpful were; 'When a Pet Dies,' by Fred Rodgers (Mister Rodgers' Neighborhood), 'When Dinosaurs Die - a guide to Understanding Death,' by Lautie Krasney & Mac Brown, 'Lifetimes: The Beautiful way to Explain death to children,' by Bryan Mellonie & Robert Ingprn, 'the Tenth Good thing about Barney,' by Judith Viorst, and one of my top pick 'Goodbye Mousie,' by Robert H Harris, and then probably the best of all is 'I'll Always Love You,' by Hans Wilhelmina,
I would not necessarily recommend, 'I'll Always love you' or 'Goodbye Mousie' because they are built on a longer relationship/bond with the child and animal. Since you had a puppy then neither of these would hold true.
With that we allowed and continue to allow our son to talk about how much he misses, 'N.,' and what he thinks about getting another dog, etc.
Good Luck