AMSTERDAM – A lone gunman shot dead six people with an automatic weapon as he walked calmly through a Dutch shopping mall on Saturday, and threatened to blow up three other shopping malls before eventually killing himself.

Panicked shoppers ran for cover or hid in shops after the gunman opened fire at random at the mall in the small town of Alphen aan den Rijn, some 46 km (29 miles) south of Amsterdam.

Dressed in camouflage trousers and a bomber jacket, the gunman began shooting in a parking lot before moving inside the mall. Ten people, were wounded, some seriously.

"I saw a woman I know walking at the other side. She wanted to enter a shop when a tall young man approached and shot her in cold blood," Marjolein Nieuwland told the ANP news agency.

"He walked calmly and shot through the windows of the shop where I was hiding," she said.

"I also saw a woman in her motorized wheelchair shot in the head, and at the Albert Heijn (grocery store) there was a young man. Also dead. Later I heard that was the shooter," she said.

Officials named the gunman as Tristan van der Vlis, 24, a local man who lived in the town with his father.

Police said gunshots were still ringing out when they arrived at the scene in response to an emergency call shortly after midday.

"Some people were running to the exit, shouting 'shots, shots'," one shop owner told NOS TV. "I saw two people lying on the floor as a young man was approaching. He was white, about 25, 26 years old with curly hair.

"He was wearing camouflage pants. I saw him get a new (ammunition) case and reload his weapon."

Public prosecutor Kitty Nooy said Van der Vlis, 24, had acted alone. He was investigated by police in 2003 on suspicion of violating weapons laws but not convicted, she said. "He had a license for five guns and he owned three," she told reporters.

Shooting at Random

Van der Vlis left a farewell letter, found by his mother, in which he mostly talked about his suicidal feelings. But it did not give a clear motive for the killings, the town's mayor Bas Eenhoorn told Dutch television.

The gunman left a second letter in his car in which he said there were explosives in three other shopping malls in the town, police said. Authorities evacuated them pending checks.

Mayor Eenhoorn told reporters that a number of children had been shot by the gunman, but he did not know if any had been killed.

Prime Minister Mark Rutte said in a statement he was "horrified" at the incident: "My thoughts are with victims, survivors, and all who have been involved in this tragedy."

Queen Beatrix sent a message of condolence at a "terrible situation," Eenhoorn told reporters.

The shootings were the deadliest attack in the Netherlands since 2009, when a Dutch national drove his car into a crowd, killing seven people and himself in an apparent attempt to hit the queen in the town of Apeldoorn, 90km (55 miles) east of Amsterdam.