The woman was doing her Thursday evening vacuuming when she saw a snake's tail sticking out from under her living room sofa.
"I screamed and ran into the kitchen but my husband said I should calm down. Easier said than done, I am still shaken," Lagergren told newspaper Stavanger Aftenblad.
Her husband Leif tried to get the snake out with a broom but decided it was wiser to call police.
"I couldn't believe my eyes, it was as thick as a man's arm," Leif Lagergren said.
Police called a security firm but before they arrived the couple found out that the snake belonged to the son of a neighbor.
The snake, which entered the Lagergren home through a veranda door, had been missing for two weeks but none of the neighbors had been notified.
The snake owner's father arrived and decided not to wait, pulling the snake out from under the sofa and cutting its head off.
Leif Lagergren said that he wanted to file charges since the snake had been at large without any of the other neighborhood residents being informed.
Dagfinn Berg of Falken Security said he thought the animal was a king python.
"We've had a few of those before, but this is the biggest one I've seen," Berg said.
