Family Dog abruptly killed: we haven't told our 3 year old yet and are unsure how to do so

I feel like the biggest garbage mom. In a haze of busyness I left our dog outside. We didn't figure this out until 7 hours later when we got home. After hearing from a neighbor, we are now 98% certain he was hit by a car and is gone. I feel so terrible about it. I've never lost a dog in that way.We actually had to put down our other dog last December because she was sick. But she was old and we had a lot of time to prepare ourselves and our 3 year old. We even managed to get through it all without having to make up any stories for her. We told her our dog had been really sick and now she was no longer in pain because she died. Sadly that meant we wouldn't see her again. Our daughter was sad but seemed to process it well.But now...... this is just so much more tragic in circumstance. She is firmly in a why stage so trying to pragmatically but truthfully explain this death to her is going to mean a lot of hard questions and disturbing answers. I'm really concerned how she would take it, because I've got 30+ years on her and am still not taking it very well. I'm very tempted to have our dog "send her a letter" saying goodbye and make up some sort of explanation. I'm really at a loss though. via /r/Parenting http://ift.tt/2vfJMqN