Dutch police stopped a potential school shooting by checking the Internet message board 4chan, and not for the first time. Police in Leiden arrested a former student of the British School after reading posts threatening to "shoot my Dutch teacher and as many students as I can." The anonymous poster included a picture of a pistol and ammunition with his message. More than 20 schools were shut down after the message was found. In 2009, Dutch police arrested an 18-year-old man for threats he made on 4chan. Minutes before a shooting at a Virginia mall this month, details of the attack were posted to 4chan.