If the judicial appraisal of his mental illness is intermittent, it is not criminally responsible to commit a crime when he is ill. Of course, you can provide the fact that your two families have been in conflict, which shows that it is possible that the suspect killed the people who have been in conflict on the grounds of illness and tried to evade criminal responsibility on the pretext of mental illness. However, these are the duties of the procuratorial organs. If a criminal case is prosecuted, an incidental civil action may be brought as a victim. When it comes to the stage of examination and prosecution, the court will definitely inform you.
But you must cooperate with the procuratorate to collect evidence.
In addition, because the criminal suspect has committed very serious and bad behavior, it is impossible to ask his family to take strict care of him. This must be compulsory, and he can only be released after being cured. Actually, it's almost like jail. If the court doesn't make such a ruling, you can appeal. After all, criminal suspects pose a great threat to social stability and the personal safety of others.
If two people die and one person is seriously injured, even if it is a rural hukou, it will cost a lot of money. Moreover, the suspect is mentally ill and needs compensation from his guardian, that is to say, his family needs compensation.