Im not going to say that i believe **(i will indicate) everything that you are saying here , but im still going to give you a reply incase it is really happening .

Please go to the police and tell them .

The police would know how to handle situations like this . Dont be afraid to tell them about the disgusting things that your step brother has been doing to you ; expose him at once so that he cant go away scott free for the things he did .

**If he really did murder your maid , how come no one knew about it except you ? Were there any evidence that points to your step brother ? Why did he kill her ?
If he did kill , its impossible that no one knows about it

If you dont speak up , he would continue to scare you with the same lines, to threaten you with your mother's lives .  This is serious and you should really contact the police since he possesses a gun . Anything can happen if you make ONE wrong move .

If you are scared that he might discover and catch you calling for help , do it outside of the house . If you are schooling , call in the school with a trusted teacher around . If you are working , call when you are beside your colleague who you can trust . 

Be strong and fight for yourself . Dont give in to him anymore. Seek help NOW .