Hard day at work

My husband is assistant manager in a record store. Today he came home almost in tears. Earlier in the day, he texted me a long string of messages (that are in french so a screenshot is useless lol) about a situation that happened.

He was in the backstore doing inventory and paper work and one of the cashiers called him to the front. A woman was trying to buy 300$ worth of kids DVDs but was paying with 10 cent coins.

Apparently, the lady came in the store and asked the cashier if she could pay for ONE movie with the coins and the cashier said yes. So the lady brought more and then when the cashier told her no, the lady started to cuss at her and agreed to do it, but called my husband in after.

He was pissed. He called the manager and the manager said that since the cashier already told the customer yes, they would have to do it for the customer.

So they spent almost three hours counting because the customer would always interrupt them and mess things up.

After that, since I was still stuck at work, he had to pick up the kids and entertain them while having what he described as “the worst headache I ever had”.

As soon as I came home he took me apart and said “I’m sorry I can’t do this I just want to lay down” so I spent the evening with the kids.

After they were asleep, I went upstairs to our room and he told me that he blacked out for a bit and feel like he’s going to puke.

He’s mad at the boss for allowing this to happen and mad at the cashier for not asking him sooner if it was okay.

I don’t really know how to support him with this... what would you have done? What’s your thoughts on this?