Who is the killer in Persona 4

The detective Tohru Adachi was the one who put the announcer and Saki Konishi into the TV world, where they were killed by the shadows.

The schoolboy, Mitsuo Kubo was the one who killed the teacher.

After that it was Taro Namatame who put everyone else into the TV, misguidedly carrying out Adachi's work in the belief that he was 'saving' them.