My brother and I accidentally damaged his clients house. What to do?

My brother owns a gutter hanging company and I went to help him today. The house was made of stucco. We put one gutter up then realized there was calking all along the back of the flashing. My brother said by removing it then he could cause some problems so he decided to not install the gutters and we just took down the one we already had up. It just had a few screws screwed into it to hold it up.

There was also a helper holding it up. It's like an arm you screw into the facia board to hold the gutter. He was unscrewing the screws. He couldn't tell were they were because he was over a deck and he couldn't see them but he could feel them. I was down the side of the deck trying my best to point them out to him. I guess after he got all the screws out, he forgot the helper was holding the rest of the gutter up. He unscrewed it and the whole gutter fell down the side of the house.

Later we noticed that the gutter left a pretty deep scratch in the stucco (the siding) and my brother wad like "well, that's what they get for building a house out of stucco". I said "should we tell the owners?". He was like "well im gonna put a shit load of caulking in it and put some paint over it and if it still looks bad then I will tell them". He fixed it up pretty good but I still think he should have told the owners.

The real estate agent was there and I guess I could have told her but I didn't want to risk tarnishing my brothers name because he's pretty well respected by his customers. Also if I told the owners or real estate agent, that would probably be the end of the relationship with my brother. I have no idea who the owners are. They were far away. I think it is one of their vacation homes but I could probably get in touch with the real estate agent. Would it be scummy if I just left it and kept quiet? What should I do? I'm mostly concerned about water getting inside the scratch that the gutter left and causing mold growth which could get the occupants sick.

My brother and I accidentally damaged his clients house. What to do?
Post Opinion