State: California

So I was hired by a business and put on a three month probation. The owner's brother started coming around to the office. I noticed right away he was rude to me, but I wasn't concerned because I did my job well. So, my manager and I ended up getting along well. She ended up taking a 2 week vacation. He started coming around more and started asking me questions about her. I believe he wanted certain answers from me but I told him I wasn't sure, I had only been there for a few weeks. He then told me that if he suspects I was defending her, he could fire me on the spot because of it. He claimed there was. "Too much drama", he basically said it was my manager who was the problem. I had been working hard, and getting more confident with my job. My co-workers were very rude to me, but I did not care because I was doing my job. I then noticed he would defend them. He claimed I was my manager’s favorite. He even threatened that if he found me texting my manager or calling her he could fire me on the spot. So, I eventually made a mistake after being very careful. He told me I was receiving a verbal warning, but that was not all. He told me he would be investigating the situation. Two weeks later, he fired me. He wrote me up, and fired me saying that I had “low performance scores on my review”. Now, after receiving copies of my review and going over them, nothing was wrong with my performance. Also, upon being hired, my supervisor told me that if I messed up, it would be a process. If I messed up once it would be a verbal warning. If I kept messing up it would eventually lead to a write up. I’ve talked to many people about this; they all assure me there is nothing I can do about this. Is this true?