BANGKOK - Police in Thailand have arrested a man on suspicion of ruthlessly killing three people, including a toddler, during a gold shop robbery that shocked the country.

Local media said the suspect is the director of a primary school. It was unclear when he was arrested.

Thai TV stations on Wednesday broadcast live as police marched the man, wearing a face mask and baseball cap, into a police station in Lopburi, about 145 kilometres (90 miles) north of Bangkok, while a crowd of onlookers shouted abuse at him.

National police chief Chakthip Chaijinda said the suspect was co-operating and did not deny involvement.

The robbery took place Jan. 9 at a gold shop inside a shopping mall in Lopburi. Security video showed a man wearing a balaclava and camouflage pants approach the store, carrying a pistol with a long silencer attached.

He opened fire at staff and passersby. A 2-year-old boy was hit as he walked past with his mother. A security guard and a shop assistant were also killed. Four others were wounded.

The robber then jumped over the counter and grabbed a number of gold necklaces before fleeing.

The incident caused outrage in Thailand, putting authorities under pressure to make a swift arrest.

Police say they would give further details about the arrest at a news conference on Thursday.