Police arrested a man who allegedly mugged three people in Thessaloniki, Greece, by threatening them with a syringe, officials said Friday. The 21-year-old suspect allegedly attacked the victims on the grounds of Aristotle University, Ekathimerini.com reported. The man allegedly forced a 33-year-old man to give him a gold chain and cross Thursday and is thought to have robbed at least two other people in the same manner in the past three months, the newspaper reported.