Funny stories when teaching chess to kids

I am struggling, but yesterday it was fun but I had a mixed feeling. Please share if you have such!

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Are Chess pieces friends for kids?

Yesterday night before we went to bed, I taught the checkmate method using two rooks against a king alone to my son (4 years old). He almost mastered it so I brought my rook to the board:

My son: "Is this rook your friend?"
Me: "Yes, he's my friend."

And he brought his rook in front of my rook, thought that it is a good opportunity to teach him it is dangerous. So I captured his rook. I noticed he was apparently shocked and saying

My son: "I am trying not to cry now..."

Tears started to flow... We ended the training and tried to bring him to the bed, but he denied. He placed every piece on the board nicely in order. He was laying down next to them and slept. Hmm... maybe I should have separated the concept of capturing a piece in a different session.