Everyone I think at one point or another shows a sign of a personality disorder, or can be under an incredible amount of stress that might temporarily have them acting in a way that might be considered bizarre. Personality disorders can be treated and aren't permanent at all, others are born with a psychiatric illness that can be treated and many times doesn't even appear until early 20's. Erratic very unstable behavior can be signs of someone that's using drugs sometimes. If anyone one of us were to go without sleep for a period of time we all could become paranoid, begin acting bizarre, even become psychotic. You really should always listen to your gut and intuition if you feel afraid, especially if it's a family member, many times relatives dismiss the idea that someone related to them could actually hurt or kill them though they have usually been threatened before and tend to not take it serious or believe someone they love would ever actually harm them, many times choosing to not believe despite lots of information that they have a family member who is mentally ill, such is the reason most people who are murdered, hurt knew the person and chose to not look at the situation objectively. So many people don't want to accept that people we are related to might be mentally ill, and the consequence can at the least deny that person getting help, and at worse can end up costing a life. Always listen to your gut and don't put yourself in a situation where you feel that you are in danger or always afraid. That's no way to live, we all deserve the right to not live in that kind of fear.