Karma (2019)

Newbie teacher Ling Shen's first day at school coincides with a student's accidental death at home. As Ling Shen gets dragged into one after another "accidental" brutal deaths, she begins to unveil the seemingly happy and vibrant campus. Shen discovers the Huaqing Club, a group of attractive and intelligent elite students, was involved in the bizarre "Mobile App Serial Murders" due to a prank-gone-wrong from years back. And the real trigger-pulling mastermind turns out to be someone Shen least expects...