I'm so sorry about your Mom.
Go with your friend and her Mom now and try and rest, try and get some sleep. Don't worry about school - you won't need to go on Tuesday whilst you are staying with your Mom's friend and that there is someone there who can take care of you during the day. I would imagine that, if she can look after you until the police can contact your Dad, that you will be able to stay with her for a little while if you have no immediate relatives in your area.
What's most important at the moment is you go with your friend and be safe in their house and you must try and get some sleep- I know it won't be easy to sleep, but do try and rest. Don't think about school at the moment.
Your school can be notified by the family that you are going to tonight and the police will be able to get hold of your Dad. The lady you're with can probably get that sorted out for you.
You mustn't be alone, OK. You must go and stay with your friend now. Go now Sophie and talk to us if and when you can. Please stay safe and stay with this family until they are able to get hold of your Dad.
Again, I'm very sorry for what's happening to you and for the loss of your Mom.