Three people have been killed and seven injured during a shooting at a factory near the Swiss city of Lucerne, police have said.
The killer, a 42-year-old man who had worked at the factory for 10 years, is among the dead.
Shooting broke out in the canteen at the Kronospan wood processing plant in the town of Menznau at around 09:00 (08:00 GMT).
A prosecution spokesperson said the shooting took place over a few minutes.
Five of the injured are reported to be in a serious condition, the Associated Press reports.
"The workers were eating a snack in the cafeteria during the morning, and there was a massacre," said a man quoted by the Swiss news website 20minutes, who had phoned the factory to check on the welfare of his father.
An emergency telephone line was set up for families of the factory's employees.
"There were three dead and seven injured, some of them seriously injured," prosecutors' spokesman Simon Kopp told Swiss newspaper Blick.
The chief executive of Kronospan, Mauro Capozzo, denied rumours that job cuts were due to be announced.
He described the man who opened fire as quiet and unassuming.
"One almost didn't see or notice him," he said, according to Reuters.
Switzerland has one of the highest rates of gun ownership in the world, with an estimated 2.3 million firearms owned by the country's eight million people, but such gun attacks are relatively rare.
All healthy Swiss men aged between 18 and 34 are obliged to do military service and all are issued with assault rifles or pistols which they are supposed to keep at home.
Until recently, many kept their weapons even after completing their military service - though rules on this have recently been tightened.
According to the Geneva-based Small Arms Survey, Switzerland ranks third in terms of gun ownership, behind the United States and Yemen.
Street gun violence is very rare in Switzerland, says Emma Jane Kirby, who recently investigated the subject for BBC News.
However, there are more domestic homicides and suicides with a firearm in Switzerland than virtually anywhere else in Europe except Finland, she says.