Charges were filed against a 37-year-old man who was linked in a bow-and-arrow attack in Norway that left five people dead.

According to the police, they had known the suspect over some concerns in the past saying that he had been radicalized after his conversion to Islam.

 “We have previously been in contact with him regarding worries about radicalization,” regional police chief Bredrup Saeverud told a news briefing.

He was asked whether the suspect might have been radicalized, he said: “We don’t know that, but it’s natural to ask the question.”

Wednesday’s assault has left four women and one man dead.

The attacker shoots arrows randomly on strangers in Kongsberg, a small town located 50 miles southwest of Oslo. He then fled when confronted by law enforcers.

The unnamed attacker is a Danish citizen, officials on Thursday said, adding that he had resided in the town

An arrow in a wall after Wednesday’s attack in Kongsberg. Credit.Håkon Mosvold Larsen/NTB, via Associated Press

Last year, concerns regarding the man’s extreme religious beliefs were reported to the police, the chief said without detailing the person who lodged the report. The authorities had followed up on several complaints, he said.

Meanwhile, the attacker’s court-appointed lawyer Fredrik Neumann told an interview that his client is subjected to mental health assessment. He is also cooperating with authorities, he said.

The attacker’s father is Norwegian while his mother was Danish, he added.

The regional police chief said that those killed in the attack were aged 50 to 70. Apart from the fatalities, two others were injured but are in non-life-threatening situations, The New York Times reported.

The attack was considered the worst mass killing in the county after 77 people, mostly teenagers at a camp, were killed by a far-right extremist in 2011.