Subtitles for this specific release are typically hosted on community databases. You can often find and download them through specialized tools or sites:

The specific group responsible for encoding and distributing this version of the film. Subtitles must be specifically timed to this group's release to prevent audio-text desync. Subtitle Availability and Usage

Swedish (original). Subtitles are necessary for non-Swedish speakers. Release Specification: DVDRip.XviD-DiGiCo

Based on real events in Gothenburg, the film follows a group of boys who use a sophisticated psychological game—rather than physical violence—to rob another group of children.

Players like MPC-HC and SMPlayer have built-in features to "Find Subtitles" and download them directly while the video is open. Play (2011)

A major database where you can search by filename to find the matching .srt file.