The incident, which occurred on Tuesday, happened while children were kept inside the Augerød daycare facility in Våler, broadcaster NRK reports.
“We consider ourselves lucky that there was no-one standing there when it fell,” Østfold's wildlife authority (Viltnemnda) director Sven Martinsen said according to the report.
The animal strayed onto the grounds of the childcare facility, which includes outdoor play areas that lead to its roof.
“A member of staff saw it enter the area, then it went up onto the roof. After that, it either fell or jumped from the roof,” Mariann Gunneng, manager of the daycare, said according to NRK.
All children were inside when the accident, which was first reported by local media Moss Avis, occurred.
After the animal fell up to four metres from the roof, wildlife authorities arrived to attend to it.
“We decided to euthanise it at the scene. Given this was a daycare, we had to take extra care. We used bullets but came close enough, so it went fine,” Martinsen said.
“An elk falling down could have hit either children or staff. There are often people at the door, so we consider ourselves lucky that there was no-one standing there when it fell,” he added.
Children at the daycare, who were reportedly ushered inside to draw the elk after it appeared, witnessed neither the fall or subsequent shooting of the animal, according to the report.
Older children were allowed to go outside to look at the elk after wildlife control had put it down.
“It was very big, and some of the children will probably speak about it in future. Things like this don't happen often,” Martinsen said.
There is no risk of children falling from the roof themselves, he added.
“It is built in accordance with regulations. But we may will have a new look at safety after this,” he said.