They know who he is, and are searching his residence, but aren’t releasing his identity yet.
Because he's not a Swede. He's a Muslim, and releasing his name or picture will inform everyone that another violent Muslim kook has murdered some Swedes. Had he been a Swede, they would have released this information immediately.
The Swedes need more of this. They need more of their people killed until they wake up and start killing or expelling the Muslims.
Their ideas about equality are just wrong, and it will take a lot of bloodshed to convince them that their ideas about equality are wrong.
Hopefully they won't lose so many people that they won't be able to stop the invasion, but they do need to lose enough to convince them that they are wrong.