One person died and two were seriously injured by gunshots in Alavus, South Ostrobothnia, on Friday evening.
Tomi Mansikkamäki, a senior officer at the Ostrobothnia police department, tells Yle that it appears that all three individuals knew each other.
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The incident took place around 8.30pm in a residence on Rimmintie. Police say the situation did not pose any danger to the public.
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In a statement on Saturday afternoon, the Ostrobothnia Police Department said that they were investigating it as a case of murder and attempted murder.
They say that a local man born in 1978 shot to death another man of the same age in his yard. The victim died immediately.
The man then shot his ex-wife, who was also in the yard. She was seriously injured and in hospital in stable condition.
The suspected shooter is custody as is the unlicensed handgun used.
It is not clear whether the suspect is the third person whom police previously said was seriously wounded.
Suspect arson attacks in South Karelia
Meanwhile authorities in southeastern Finland are investigating a string of suspicious fires early Saturday. There were at least half a dozen fires in Imatra and Lappeenranta between roughly 2-5am.
Police in South Karelia believe that they were all intentionally set.
The blazes destroyed several outbuildings housing waste facilities and many mailboxes as well as damaging at least three cars.
Most of the fires were in Imatra, on the Russian border, but one car was also burned in Joutseno, about 20km away in the neighbouring municipality of Lappeenranta.
Police are investigating the cases as vandalism but note that other charges are possible. They are asking the public for any information related to the incidents either by email (firstname.lastname@example.org) or phone (0295 414 559).
5.04pm: Updated with police statement on shootings.