Adopted a cat, he attacked my dad and I

A friend of my brother had a cat (1.5 years old, male, black, not neutered) that she could no longer because her 3 year old son started harassing the cat. We decided to adopt the cat after we saw that he acted friendly towards our dogs and our other cat. After the original owner left our house, we put the cat in a medium sized room so that he could acclimate for a few days before being let out into the rest of our house. While we were getting the cat settled in, my dad was petting him, and the cat attacked him and drew about a quarter of an ounce of blood from him. A few minutes later, I was in the room and I pet him on the head. I stopped, sidestepped for a few feet, and then turned my back on the cat to leave the room. As soon as my back was turned, he attacked my leg. Whenever we get close and try to pet him, he attacks. However, he will walk up to us and rub against us. This is all happened in the span of 30 minutes. Note that the cat has never attacked anyone before. Is this normal?

Edit: the cat attacked my dad unprovoked. My dad let the cat walk up to him, started to pet the cat, and then was attacked after a few seconds. The cat will walk up to us, rub against us, and then attack without being provoked. Needless to say, we are going to find a different home for this cat.

Edit 2: I don't want to have to rehome him, but he has already attacked me twice and my dad seven times. As I type this, I'm doing my homework right now in front of him, and he likes to walk by for the occasional petting, but we're afraid he will attack our other pets. He is a sweet cat, but we may not be the right fit. I'll talk to my dad to see about letting me bond with him for a week before we begin to look for another home.

Edit 3: thanks for all the feedback! I really appreciate it. I am, by no means, a cat person. I do, however, think that this animal deserves another shot before we risk him ending up in a shelter. I've started to bond with him, and I hope he doesn't blow his one shot. I've been given a week from my parents to bond with and tame him. I hope it goes well.