My daughter raise goats, the rott they have about 1 year old got out of the pen and attack the baby goat. She had the vet take care of the goat damage to rear leg, was doing just fine.

THe ROtt got out his pen again and got into the goat pen with the same goat in it and attack him again. Hadto put the baby goat down too much damage this time.
Does anyone have a clue why the rott would do this?

I think it is partly just being a dog. They all retain some of their ancestor wolves prey drive. I would expect less of it from a breed with a herding heritage, but many modern dogs are far from their original traits. I have had Labs that hated the water.

The other part of the problem could be boredom from being out in a pen by itself. That is no place for a dog. They belong in the house with their pack, the family and any other pets. There are solutions to chewing and fouling the house. Even shedding can be reduced by frequent brushing. Your daughter could post specific questions here.

I had a rottweiller growing up, and had to deal with many of his 'instincts'. Having one gave me and my family a bad rep, because many put the breed up there with pitbulls. Measures have to be taken to make sure the pup is properly contained. Cemented flooring with a sheltered fence around it will be fine, but if he is to be put out there and never in the house then other comforts have to be added in. But I really do suggest you bring the dog in, especially if you want him to listen to commands. He is still young enough to learn. They are, believe it or not, dogs that need a lot of attention, get stressed easily when left alone for long periods and this rottie is only a year old, to be placed out in this weather for prolonged periods is a no no.

Hunger, being cold, or feeling abandoned may have been the culprit.

It is a dogs instinct to kill and eat what they kill, and at that point that dog found a goat very appetizing.