SINGAPORE - A man who head-butted a 10-year-old boy at a bookstore was given the maximum fine of $5,000 on Wednesday.

Phillip Ong Kuan Ming, 32, who works in human resource, admitted to causing hurt to the victim at the bookstore in Queen Street on April 12 this year.

Investigation showed that Ong approached the victim that morning and wanted to speak to his parent with regard to an issue between the victim and Ong's son.

At that time, the parent had not arrived.

While the victim was waiting for his father at the bookstore, Ong went up to the boy and head-butted him on his forehead.

The victim suffered a 2cmx2cm haematoma - a solid swelling of clotted blood within the tissues - to his forehead as a result of the assault.

His father lodged a police report the same day.

Ong's lawyer Mansur Husain said in mitigation that what his client did was "totally out of character, out of sync with his personality."

He said until today, Ong was not able to give a reason why he did what he did.

The lawyer said his client stayed until the victim's father arrived, and had reimbursed the father for the medical expenses.

District Judge Ng Peng Hong noted the victim in this case was a young boy. He said fortunately, the injury was not serious, but he had to impose a hefty fine to reflect the seriousness of this case.

The maximum punishment for the offence is two years' jail and a $5,000 fine.