Ok, time to crush Renekton and rescue Amumu.
Inform the Authorities
Call the police and child protective services. Tell them that Renekton hit you, that you want to press charges, and that you are worried for Amumu’s safety because of his father’s sudden, violent anger.
Do Your Research
Learn about the child welfare and assault laws and talk to a lawyer, who can offer a free, brief intitial consultation about your rights and answer at least a few easy questions. Call non-profit organizations as well, since they are under less pressure to turn callers into clients and may offer more help. Follow their advice.
Search the Internet for any public records about Renekton. Anyone so violent as him might have been arrested for at least a misdemeanor somewhere, likely disorderly conduct or petty battery. Record this information and its source.
Next, talk to Annie about Amumu. Tell her what happened and that you worry Renekton is abusing him. Ask him if he goes to school with her and what he has said about home. Write it all down.
Update the Authorities
Write to the police, child protective services, and Amumu’s school, informing them of what happened, relaying your research with copies of the public records and notes of Annie’s comments attached, mentioning in each letter that you have informed them all. Deliver the school letter personally by requesting an appointment with the assistant principal to discuss events having raised serious concerns about the safety and well-being of a student (Amumu).
Build Your Case
The ultimate goal of these efforts is to persuade the authorities to take Amumu from Renekton and give him to you. If you can gather evidence that he is a violent, angry man with a criminal past and who mistreats the boy, then it should be possible to argue that placing him in your home would be better than keeping him with Renekton, especially if you can persuade Amumu that he shouldn’t want to stay.
Move Away
Renekton will try to kill you, Amumu, and possibly himself if your attempt nears success. Even if you can put him in prison for abuse, he will only leave it angrier, more violent, and better prepared to act than when he entered. You two will need to move away, change your names, and act like different people if you should hope to survive. Get a protective order to make yourself feel better and give the state a break if they’ll have to prosecute him for murder.