WARNING: This video contains disturbing content. Viewer discretion is advised. School violence is making headlines in Europe and raising questions about the influence of social media, as Poland sees two knife attacks in just two days. One person is dead, 11 others are injured, and there may be a third attack that was prevented. As Mike Armstrong explains, investigators are looking at whether the incidents could be linked to an online challenge. For more info, please go to https://globalnews.ca Subscribe to Global News Channel HERE: http://bit.ly/20fcXDc Follow Global News on X HERE: http://bit.ly/1Toz8mt Follow Global News on TikTok HERE: https://www.tiktok.com/@globalnews.ca?lang=en #GlobalNews