As of 2 days ago (18 Oct 2021) UK media is saying that the victims were not killed with the bow and arrow.
The police have said that while he did shoot at people with his bow and arrow, at some point he either ditched the bow or lost it.
The injured, but not killed, victims were shot with arrows.
The dead victims were stabbed with a "sharp object" but the police would not elaborate further.
The people attacked were random, according to the killer.
Mental illness, not converting to islam, is the main cause, but the police refuse to comment further. It reminds me of how, in the UK, they can be shouting islamic terroristic phrases while committing the crime and the police and government tell us it had nothing to do with islam.
The killer is still being called a "Danish citizen" by the police.
NOTE: I have read various UK news outlets of various political leanings and the above is essentially the same in all of them.