My poor ducks got attacked

I had two khaki Campbell ducks (5-6 weeks). I have been keeping them in their brooder in a small room attached to the house. The night before they started hopping out of the brooder (I used a large plastic tub with a clamp lamp). I wanted them to spend more time outside so I wouldn't have as much to clean off the floor. I set them in their pen this morning and later my husband and son went to play with them. He found one dead and the other appeared to have a gash on his face. He didn't get into detail about what the dead one looked like since I was attached to that one and pretty upset. I ended up putting antibiotic on his cut and putting him up to rest. He appeared to be okay.
Later tonight I was looking at him with my neighbor and we noticed another wound under his wing. I also noticed he was walking a little weird. One foot kept going over the other. My husband does not think it's broken because he swims and walks with it. I gave him a bath, put more antibiotic, and put electrolyte in his water. I think I will get oral antibiotic tomorrow as well. He seemed to enjoy the bath, is eating/drinking/pooping okay, and bleeding stopped. He is quieter sadly. I'm guessing shock. I feel horrible he had to watch his buddy like that. I am not sure if I should get him another duck/duckling or try and raise him as a house duck.
I am not sure what got to them. I set them out pretty early and my husband found them around 11am. I didn't think a cat would take them on but that's what I'm leaning toward. My neighbor said she saw a huge raccoon recently but I didn't know if he would be able to get over the fence. I don't know raccoons though. We are currently looking to get a house off a lake so any suggestions for defense from the predators would be great too.
T.I.A
(Sorry if the pictures are hard to see sometimes. I think it's the darker color and I didn't want to scare him too much by handing him and putting out his wing)

does the pen have chicken wire around it and on the top of it? if not then u need to do that, plus u need to outline the bottom of the pen in cement bricks/blocks , but if it s not chicken weed do that first and double chicken wire around the bottom of the pen. u know this is kinda weird i jus gave this advice to somebody who was wondering what to do when his ducklings hatched. But it would be very beneficial if you were to wrap that pen up in chicken wire like to where you no its safe , give a whole professional inspection before you think your done though

is their pen like a dog pen or like a play pen, like for puppies or like one of this chain link kennel pens, Please post a pic