My dogs killed the neighbors cat?

Ask: I honestly feel so awful because it's Christmas, and they have kids. The cat never climbed my fence before, until tonight. I've got a cat also that doesn't like other male cats and when I let my dogs out he goes out with them. My yards pretty huge and the porch lights doesn't shine over every part of the yard so I didn't see the cat when I let my dogs out. 

 I'm pretty sure that the cats got into a fight first and both of my dogs jumped in to protect him and ended up killing the cat before I could stop them. I don't think they heard the noise because it was over soon as it started. I mean they've never shown any aggression towards the other random cats that they've come across, I just don't understand.

Though I don't know what I should do? Should I tell them what happened? That'll ruin the holidays for them and I don't want that. Or just bury the cat now and tell them after the holidays.

Answer:
Reza:  Let them know about it but make sure to tell the parent/s outside away from the kids. They can decide whether or not they want to tell the kids right away. Make sure to apologize - not for your dogs actions but more for the fact that you do feel bad that they lost their cat. Tell them exactly what happened and that you didn't know what was happening until it was too late.

Just remember it isn't your fault. They should know what can happen to outside cats, but don't argue with them about it. If they try to argue or get mad just say you're deeply sorry about it and walk away. 

Danny: Tell them what happened. Warning, they're probably going to demand that you put your dogs down. You shouldn't be required to because that cat was being aggressive, and was also on your property, but I'm just giving you a fair warning. This will likely ruin the relationship you have with your neighbor. 

Elaine: TELL them, no owner wants to be waiting and worrying about where their pet is. Do not wimp out and hide the body. Go over, get one of the adults, give them the cat wrapped in a towel and tell them you're sorry.

Look, if someone hit your dog on the street would you want them to shove it in their car and dump it in a ditch and not tell you, leaving you to worry and panic over what happened to your dog? Be considerate of the other owners. 

StarOfDarknes: Was your dog properly confined in the back yard? Then you owe then nothing what so ever. Their cat was allowed to run loose and since they were so lazy and cared nothing for the cat and let it run loose, they can't do a damn thing to you. By LAW its their fault 100% since they let it run loose and it wasn't on a leash or confined.