A 10-year-old boy in Hong Kong was arrested on Wednesday for armed robbery, after he and two older boys allegedly made off with 20 luxury watches worth HK$3.7million (S$643,000) on Monday, reported Hong Kong news outlet The Standard.

Sources said he wielded a hammer during the heist.

His accomplices are not much older. One of them is 14 and the other is 19.

According to The Standard, the 10-year-old and 14-year-old were wearing their school uniform when they walked into the VIP Station store along Canton Road in Tsim Sha Tsui district.

Together with the 19-year-old, they allegedly used a butcher’s knife and a sledgehammer and smashed display cases in the store, before making off with the watches in 30 seconds, Superintendent Alan Chung Nga-lun of the Kowloon West regional crime unit said.

A female employee of the store suffered minor injuries on her hand and was taken to the hospital, The Standard reported.

The 19-year-old, who is of Pakistani descent, was arrested on Monday.

The younger boys were arrested on Wednesday.

The 10-year-old had reportedly received HK$5,000 as a reward for skipping class to take part in the robbery. He was taken back to the store for crime scene reconstruction on Wednesday afternoon.

Another boy, a 17-year-old believed to be the brother of one of the suspects, was also arrested for allegedly misleading police by claiming to have no knowledge of the robbery.