A 22-year-old man suspected of killing three people at a shopping centre in Denmark's capital Copenhagen is due to appear before a judge for questioning.
Two Danish citizens, both aged 17, and a 47-year-old Russian citizen were killed in Sunday's attack.
The suspect had mental health issues and there is no indication of a terror motive, police say.
He had a rifle and a knife and his shooting was random - "not motivated by gender or anything else" - they said.
Speaking to reporters on Monday, police chief Soeren Thomassen said they believed the suspect - described as "an ethnic Dane" - was acting alone and was not helped by anyone else.
He added that the suspect was known "peripherally" to police.
Police are also investigating videos of a young man with weapons which have been circulating on social media since Sunday, and believe them to be authentic.