Hi, I'd like to help you with your question.
There are many reasons a child acts out. For some children, their personality is the cause. They are naturally aggressive in nature and see nothing wrong with hurting others. For other children, it is a learned behavior. They witness violence or are the victims of violence themselves. And still other children have biological reasons for acting out. They may have been born to parents that used alcohol and other drugs (the father's use can also affect the child's development if he used before the child was conceived). There are also learning disabilities and other organic causes.
Some of the possible causes of aggressive behavior include:
Inadequate verbal and expression skills
Lack of routine
Have your son and his wife watch the child. Note when he acts out and what is going on around him at the time. Was there a trigger? Was the child over tired or stimulated too much? They should look for a pattern in his behavior. This will help them and a professional help identify the problem.
Your grandson needs screened to see what the cause might be. A child psychologist or other qualified professional should do a full evaluation to see what might be causing this behavior. Talk to his doctor about a referral to a child psychologist. Or contact your local hospital or clinic for more guidance.
Also, is your grandson getting consequences to his behavior? Children are rarely able to understand how to control their own behavior so adults need to set limits. If he does not respond to simple punishments, he may need more intense corrections. Also the punishment must fit the action. For example, if he yells at someone, a time out may be enough. But if he hits, then he has all his toys taken away for a day. Some children need consistent rules and enforcements in order to bring their own behavior under control.
You can also help your son and his wife try these steps when their son acts out:
Immediately remove him from the scene- if he becomes upset or aggressive, take him out of the situation right away. Don't give him another chance or warn him. Removing him helps him pinpoint when his behavior becomes too much.
Don't yell- keep your voices even. Change your words and tone, but not the level. When you yell, kids can tune you out easier. If the child acts out, say in an even and serious tone, "You will leave with me right now". And ignore any protests.
Set rules and review them often- make the rules simple and straight forward. No hitting, no yelling etc. Talk about consequences if the rules are broken. That way, he is not surprised when he is corrected for his behavior.
Here are some other resources to help you:
The Difficult Child: Expanded and Revised Edition by Stanley Turecki and Leslie Tonner
Setting Limits with Your Strong-Willed Child : Eliminating Conflict by Establishing Clear, Firm, and Respectful Boundaries by Robert J. Mac Kenzie
You can find these books on Amazon.com or your local library may have them for you.
I hope this has helped you,