I have a boxer cross that answered the door with hackles and something happened to her. She fell down on her side, arched her back as if stretching, shook a little and passed out peeeing over the floor. I waited until she started coming around and then I carried her to a more comfortable place. This is the first time she s done anything like this. She is 12 years old.
Your child probably suffered from micturition syncope which can happen when the blood rushes to the bladder during passing of urine and in the process blood flow to the brain is reduced and fainting occurs. The consciousness returns soon after when the child comes in recumbent posture after fainting. You need not worry about it but if it keeps recurring, you will need to get the child investigated.