Of course somebody should've called the police by now, but realistically, who would do it?
Miho? She's basically kept hostage by Seo. One wrong move and her life will be on the line, and she's not the selfless type.
Satsuki? She's too busy trying to save other people, and also deliberately shutting down her own thoughts as otherwise she'll break.
Vice Prez? Her boyfriend got murdered in front of her and she's likely a psychopath, seeing her reaction to Michiru going bzzt. Might be plotting revenge on Seo or just mourning her loss, for all we know; either way, we can't expect her to call the police either.
That's it. There are no other witnesses to Prez murder. Maybe Sensei will call them next chapter as he realizes that explosion couldn't have been a mere prank, but yeah.