My sons 1st bestfriend is dying

My 12 year old lab has cancer and is being put down tomorrow. My heart is completely broken😔 my son loves her soooo much and Everytime he goes somewhere he screams “NIL” which is short for Nilla, for her to follow him. I have a lump in my throat just thinking about my little boy getting so excited to see her in the morning and her no longer being here and him having to wonder where she went. Never really pictured her not being in our life so I’m just not prepared for this. Ugh