A fellow employee used a chair to hit the gunman who on Wednesday shot nine co-workers, killing three of them and injuring six others at a wood processing plant in the canton of Lucerne, fresh news reports say.

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The employee struck the 42-year-old gunman, a machine worker identified as Viktor B., on the head, newspaper 20 Minuten reported online on Thursday, citing information provided by a reader with contacts at the Kronospan plant in Menznau.

The action is credited with preventing the shooter, identified as Viktor B., from claiming more victims, said the informant, adding that it was an act of “great courage”.

Police have not confirmed yet how the gunman died but reports indicate that he shot himself.

Meanwhile, Lucerne police confirmed that a fourth victim from the shooting spree died in hospital early Thursday.

Four other victims injured in the shooting incident were described by police to be in serious condition.

The shooting occurred at around 9am during a coffee break when for reasons unexplained Viktor B. began firing a handgun at co-workers in a workshop, hallway and cafeteria.

Police identified the gun as a Swiss-made semi-automatic pistol.

The Sphinx AT30 model firearm, made in Nyon in the canton of Vaud, is not a weapon used by the Swiss military, police spokesman Urs Wigger told the ATS news agency.

Investigators are trying to find out how the killer obtained the gun, which has not been in production since 2000.

The gunman, who had worked at the plant for 17 years, was described by a company official as a quiet, calm person without a record of violence.

Swiss newspapers showed photos of the married man, reportedly a naturalized Swiss citizen with Kosovo roots, with two children.

The Neue Luzerner Zeitung quoted a colleague as saying the man’s behaviour had changed over the past year and that he would sometimes talk to himself.

“He was weird but we never thought it would come to this,” he said.

The Kronospan plant, the biggest employer in the town of 3,000 people west of Lucerne, announced that it was closing for two days.