The officer was just starting to acclimatize to the intense heat, when through the haze, he realized that one of the men sitting next to him was a drugs offender who had gone on the run after being sentenced to prison.
“By a coincidence, and rather amusingly, they both recognized each other in the sauna,” Christoffer Bohman, deputy police chief in the Stockholm district of Rinkeby, told Swedish state broadcaster SVT.
“It's easier to take action when you have your colleagues with you, and all your tools and equipment. This was as stripped-down as it gets – in more ways than one.”
The arrest was potentially dangerous as the wanted man had also been found guilty of attempting to assault a public servant.
The officer was saluted in a post on the Rinkeby Police's Facebook page under the headline “naked arrest”.
“To our dear colleague who kept your head cool when it was heating up to a potentially dangerous situation, despite being on your day off and relaxing in a spa,” the post reads.
“Despite finding yourself in a packed sauna with a wanted criminal, you kept your wits about you and carried out an arrest while considering the needs of all.”
The post signed off: “We are everywhere. Even if you don't see us, we are there.”