The man arrived at the Täby police station on Thursday morning and told officers he had killed his wife, the Expressen newspaper reports.
Officers were dispatched to the couple’s home, where the woman’s body was found.
According to police, the woman was killed from a violent blow or blows from a foreign object.
The man who confessed to the killing had been convicted in 2007 for the attempted murder of his wife and sentenced to court ordered psychiatric care.
The man was serving his sentence at the Löwenströmska mental health facility and was away on temporary release when the killing took place.
“What’s happened is just awful,” said Löwenströmska’s head doctor Kaj Forslund told the TV4 news website nyhetskanalen.se.
He added that he plans to investigate whether or not it was appropriate to grant the man’s leave request.
Despite his attempt to kill his wife in February 2007, the man did not have a restraining order barring him from visiting his wife.
The exact motive for the killing remains unclear, and police say there are no signs that the man was under the influence of drugs or alcohol at the time of the killing.