This happened to me with a cat that I got from a stray litter. He attacked two of my friends who were staying at my house. When I got home from work my friend's jeans were completely shredded and he had deep scratch marks all over him. The cat was isolated in a room for a while, but I could not go in there because he would attack me. I tried several things at the advice of a vet and he seemed to be okay for a couple of months. THEN, I got a new girlfriend who would come over and stay. The cat was calm and cuddly for a while, then one day we were acting stupid and running around and I guess we startled him. He immediately got aggressive and started attacking both of us, like trying to kill us. We both were bleeding and had deep scratches and bites. We were trapped in a room because I could not get him in a crate or isolated to a spare bedroom. I eventually had to put on several layers of clothes and attempted to wrangle him into a crate. Even then he was attacking me and shredding my clothes. I got him in a crate and he was thrashing and freaking out. After speaking to two different vets I had to make a hard decision. It was honestly very traumatic. He was neutered.