Although you didn't ask, here is some advice about the consequences of YOUR actions: Don't take any more scooters from kids! You could wind up in jail yourself.
This kid's mother obviously doesn't believe her little darling could do anything wrong, so telling her about possible consequences of his actions isn't going to do any good. If she had called the police to complain about that nasty woman who took away her poor baby's scooter, you very well might have been arrested.
Contact the management of your apartment complex and ask them to do something about it. If they don't, or if you are threatened, call the police.
You may also be able to get a restraining order to stop the harassment. Check with the clerk's office at your local courthouse. They should have a packet with all of the necessary forms and instructions.