The swan was killed with a targeted shot by city authorities in Horw, near Lucerne, after its latest attack resulted in a broken collarbone for a lake swimmer.
The animal had attacked another person a few minutes earlier and had been known to pose a threat to humans for six weeks with its increasingly aggressive behaviour, said a statement by the Horw municipality.
Its attacks included an attempt to drown a swimmer by sitting on him, a report in the 20 Minuten newspaper said. In recent days, the animal had also attacked another swan family with cygnets.
"This is extremely dangerous and can lead to drowning," Otto Holzgang, a wildlife biologist for the local agriculture and forest department, told the 20 Minuten newspaper. Another swan in the area grabbed headlines in 2008 for its aggressive behaviour.
"Maybe it is the same animal - but we do not know for sure," Holzgang told the paper.
According to biologist Hans Schmid of the Swiss Ornithological Institute on Lake Sempach, such behaviour is unnatural for a swan, especially when its young are old enough.
"There is no other solution than shooting," he was quoted as saying by 20 Minuten.
However, not everyone agrees with putting the animals down as a solution to the problem.
"That's an exaggeration – he was only defending his territory," 27-year-old Horw resident Steven Langer was quoted as saying.
The Horw municipality statement added that the dead swan's cygnets are sufficiently well-developed to survive without their father.
Barriers and warnings on the lake shores have not discouraged swimmers from taking dips in the lake’s blue waters. City lake swimming is very popular in Switzerland, with lakes and river banks in Geneva, Bern, Lucerne and Zurich constantly crowded with bathers in the summer months.