Helen Fitzgerald is the author of "The Grieving Child: a parents guide.  She is the director of a grief program, lecturer, and death educator as well. 

"How do you explain a suicide to a child? This is a tough one. Your child needs to be told about the death as soon as possible. She needs to be told everything you fear she will hear from relatives, friends and their parents. She needs to have this information from you. … Again, this is an opportunity to bond with your child and to underscore your intention always to be just as honest as possible with her.

Start by putting your child in a position where you are touching each other, perhaps on your lap. Children need lots of touching to feel secure. … Tell her you have something very sad to tell her and that sometimes when one feels sad one cries, and that crying is okay. You might add that talking about this sad thing can cause you to cry, and that when you cry you need hugs. This will give her something to do when you cry and she will fell less frightened. Now you must go on to say, “Daddy died today.” Usually the child will ask questions. Answer them as they come and as simply as possible. Don’t give too much detail. Then comes the question, “How did Daddy die?” Your response may be something like this: “Sometimes we can’t understand why people die in the way they do. When someone dies of cancer, heart attack, or an auto accident, we can understand it more. But sometimes people die in a different way. They do it to themselves. Do you know what that’s called?” (Children will hear the word “suicide” from others; it is better if it comes from you first.) You might continue, “Sometimes people have an illness of the mind that causes them to kill themselves. They have it; you don’t. I don’t. It’s hard to understand, and it has nothing to do with me or you. I didn’t and you didn’t do anything to cause this.” Invite your child to come talk to you if she starts feeling bad or responsible for the death.

The next dreaded question may be, “How did he do it?” Again your child needs to know, but spare the graphic details. You might say, “This is hard for me to tell you, but I will. He had a gun and he shot himself.” Or “He took a rope and hanged himself.” Or “He went into the car and closed all the windows and kept the car running and the poison gas killed him.” If your child asks, “What did he look like?” You can start with something like, “What do you think he looked like?” This may give you some insight into your child’s imaginings about this tragic event. Some children will demand to know more of the details. These can be given in simple form without going into great depth. If too much is kept hidden, however, I worry about what your child will imagine. Sometimes their imaginings can be worse than the truth. Again, I want to emphasize the importance of inviting your child to come to you if she has questions or hears disturbing comments that require factual answers.

Children find a suicide death confusing. One little girl wrote a “pretend” letter to her father who had killed himself, saying, “You said you loved me, but how could you do this to me?” The mother of this child explained that her father did love her but that because of the illness he had had in his mind, he could not think clearly and his thoughts were jumbled. She also reassured her daughter that her father knew she loved him.

Because suicide is such a difficult subject to discuss with a child, don’t hesitate to ask for professional help if you find the going more than you can handle."

From The Grieving Child:  a parent's guide