Believe your child. Even if you do not for some reason, pretend that you do. False reports of child abuse or sexual abuse are incredibly rare and the damage done to a victim who is not believed can be very large. Even if the alleged offender is your boyfriend, husband, brother, pastor, nephew, or life long friend. Believe your child. Understand that talking about what happened to them may be incredibly hard, embarrassing, or painful. Don't push them to say more than they want.
You want to try to present a calm, empathetic, and caring demeanor. If your child feels like you cannot handle this, they may shut down. Do not let your child hear you yelling, screaming, or venting to others about the abuse. Do not threaten to kill the offender. This is a natural reaction; however, all your child is hearing is, I may loose my parent too. They might go to jail or get hurt. Your goal is to support your child, provide safety, reassurance, and love. Thank them for telling you. It is ok to cry, to show emotion, or to show anger, be authentic, just try to keep it about them.
Report it to your local police or department of social services if it has not already been reported, especially if there is any chance the perpetrator will be around your child or other children in the future. Families often fear involving authorities; however, this is typically the best way to protect your child and other children from future offenses. This report does not register the alleged offender as a sex offender, that can only happen in a court of law if they are found guilty. This call only protects other children and your child while you and your child and the authorities "figure things out".
Schedule a forensic interview as soon as possible, especially if you are pursuing legal recourse. This is a specialist who works with your child to gather as many details as possible about what happened in the most therapeutic and safest way possible. Leading questions and children attempting to "do the right thing" or avoid family conflict can lead to false memories, false recanting, unreliable testimony, and changes in the abuse timeline. Try to avoid questioning your child too much and just tell them they can tell you whatever they want or need to. A forensic interviewer should be the first person your child talks to other than you if at all possible. They can share the info they acquire with law enforcement and child protective services. Child Protective Services workers and law enforcement officers are rarely trained in the appropriate way to interview an abused child. It is ok to avoid having your child talk with them until the forensic interview is able to be conducted.
Schedule a consultation and/or evaluation with a therapist. This consult is for you and your child. The therapist will typically ask you questions before your session and then will likely meet with you, you and your child together, and your child alone. Lots of parents ask what they should tell their child. Tell them that just like there are doctors that help your body heal when it is sick, there are people who help you heal your feelings when something or someone hurts them. Do not pressure them to "tell the therapist everything" or tell them they will have to talk about it, just keep it short and honest. Tell them the therapist is there to help them. The therapist will make a recommendation on if, when, and how often therapy should occur. True PTSD does not develop until later, but that does not mean therapy sooner is wrong, it depends on the situation. Some young children can actually be re-traumatized by poorly executed therapy or evaluation, so make sure that you go to a trauma specialist who has advanced training in working with children. Trauma Focused Cognitive Behavioral Therapy (TF-CBT) is highly recommended for children with trauma. EMDR and Play Therapy can also be a very good fit. Some children will not need therapy, but their parents would benefit from support and coaching to work through supporting their child as well as to know what to watch for in the coming months if they start to develop trauma symptoms.
Seek support for yourself. Whether this is therapy just for you, a support group for parents online or in person, or talking to a friend who has gone through something similar. You do not have to go through this alone.