My Neighbour's Cat Was Killed And I Want To Know If Anything Can Be Done To The Killer

Hello,
Before anything, I want to state that I live in Portugal.

I come asking for help, because as the title states, my neighbour's cat was killed. It was a very, very sweet cat, he would greet anyone and wasn't afraid of asking for pets. I live in a small town, so everyone knows each other.

For the purpose of the story, I'll call the cat's owner Eight (his house number) and (who I suspect to be) the killer as Five (also his house number).

Five has a history of hurting cats. In one occasion, my cat came back home limping and with bloody urine, whilst on another occasion, he had journal paper filled to the brim with rat glue stuck to his thigh and back. These were both confirmed to be done by him, as we confronted him.

Eight's cat and my cat look similar, they're both European shorthairs, but 8s cat had a green collar, whilst mine didn't.

Now, here's why I suspect he killed the cat. On the edge of the sidewalk, I saw a few blood drops, the biggest measured about (eyeball) 1cm in diameter, originating near his property and the smallest drop (again, eyeball) measured around 0.5cm in diameter nearing my gate. The cat was found in the middle of the road, placed neatly, with both hind legs together and both front legs also together. It looked as if it was sleeping peacefully.
When I saw the cat, Five was outside, asked me if that was my cat, with sort of a small smile, or a smug look. When I told him it wasn't, because mine doesn't wear a collar, he answered with a "Oh" and went home.

From what I gathered from other neighbours, although they hadn't seen anything, they thought that the cat got run over by a car.

Eight's wife came to pick up the cat's body and we later heard from them that the cat only suffered damage to the head and had missing teeth, which makes me think that he was killed, and not run over.
I told them everything I theorized and they seem to agree with me.

The reason I'm so invested in this is because we're close to Eight's family and I believe that Five wanted to kill my cat instead. We're afraid of letting him go out because of Five.

So, again, I come to ask; Is there anything that Eight and I can legally do in this situation?
I'm angered and emotional, but there must be something that can be done...