The child needs the help of his parents to channel his aggression.
At any age, it is normal for the child to be able to express aggression from time to time, especially in the very young. As certain parts of his brain are not developed enough, he needs adults to learn to better control himself.
Aggressive behavior is explained in children by a lack of cerebral maturity which does not yet give him sufficient capacities to reason and communicate without violence. As he grows, he manifests less and less physical aggression because he realizes that he can hurt with violent gestures.
It is therefore for him a means of communication to claim more attention or affection. Aggression can also be expressed by mimicry of aggressive behavior by adults or children, or to express concern about changes, arrival of a little brother or little sister, separation, bereavement, change school …
This behavior, just like in adults, can also appear in case of fatigue or overstimulation after a long period of play for example. Finally, we can observe him during severe punishments or when he understands that he gets what he wants with his hostile behavior.
Adults’ behavior in the face of aggression allows them to help them control their emotions. Therefore, it is imperative to lead by example by remaining calm and firm and by indicating to him that his behavior is not acceptable. Explain the consequences of their actions and encourage them to express themselves in simple words about what they are feeling. You can also ask him to console the person he typed for example or ask him to withdraw for a moment to calm down.
If really after 3 years you still notice frequent aggression, do not hesitate to consult a health professional to better understand what is going on.