B.F.
Edit after up date: I am so happy your mom is ok! I am also glad she had a talk with you. I understand you love your mom very much an that made you very worried about her. Think of all the things you did right. You went next door and got help. You took care of your sibling. You reached out to us. You are maturing and next time something happens, you can handle that too. Be brave, you can handle it!
Sweet heart, she will be getting the help she needs. Everybody has accidents. I fell down the stairs last year and broke a rib but I am fine now.
It's not your fault, it's an accident. I am sure she would not want you to be freaking out. Take some deep breaths. Wash your face. Is there someone you can call to come stay with you? A relative, a friend's mom? It's going to be ok.
I am sure your dad is on his way to your mom. Listen to the mom that is there. Talk to the God you celebrate tonight. He has told you he is a merciful God. He loves both you and your mom. Trust Him. It's going to be ok.