Telling younger child baby is gone.

Has anyone had to tell their younger child the baby was gone after a miscarriage/chemical? I had no issues with my first pregnancy so I did not think twice about telling our son about the baby this time - he has been so excited- but I started miscarrying this morning. We are Catholic so I’ve debated on telling him the baby was too sick and had to go be with Jesus, he knows who Jesus is, but not sure...Anyone have any advice? Next time I’m going to wait to tell him so we don’t have to go through this again, this is heartbreaking. Thanks in advance!