The animal was killed by a blow to the neck as a direct consequence of its attack on the girl, reports broadcaster NRK.
“It has been taken care of, to put it one way,” acting spokesperson for Os Municipality Laila Reiertsen told the VG newspaper, which was first to report the fate of the animal.
The swan chased after the girl and attacked both her and the boat she was sitting in, according to VG's report.
After the swan managed to get into the boat, the girl was frightened enough to jump into the water and swim to the shore, writes local media Midtsiden.
“I cannot go into details about how the swan was put down, other than that it has been done,” Reiertsen told NRK.
Initially scheduled to be put down by Os Municipality on June 23rd, the swan – which has been a source of both sympathy and anger among local residents as debate about its fate rolled on – was later granted a stay of execution after action groups proposed ways to relocate it.
Authorities has said that they would attempt to relocate the swan from the town of Osøyro, so that it could be spared.
Reiertsen declined to confirm whether Wednesday's attack was the primary reason for the swan's fate.
“A resolution was made earlier in the summer which is still valid. We were then presented with an opportunity to see the resolution through, and decided to go ahead with it,” she told NRK.
But the Bjørnefjorden Agricultural Office (Landbrukskontoret i Bjørnefjorden) confirmed to the broadcaster that the swan was killed by a blow to the neck, and that the measure was taken as a direct consequence of Wednesday's attack.
The swan was calmly and peacefully captured, encaged, transported away and put down,” agricultural office leader Øystein Svalheim told NRK.
“It was clear from the initial resolution that if a new incident occurred, we would be obliged to implement quickly,” Svalheim added.
Reiertsen admitted that she expected strong reactions both locally and nationally to the decision to put down the Harbourmaster.
“Seeing the range of feelings that have characterised this issue previously, we can expect both kinds [of reaction],” she told NRK.