Fifty teens were arrested Friday night after Philadelphia enacted a 9 p.m. curfew on weekends. The city's mayor, Michael Nutter, called for the new regulation in order to curb recent mob attacks, which teens have organized using social-media tools. Teens face up to a $300 fine for their first offense; parents may be fined up to $500 for their child's second offense and could be charged with child neglect if they fail to collect the arrested teen. Nutter blamed recent violence on a "relatively small number of complete knuckleheads." He also spoke to parents, saying, "Get your act together. Get it together, right now! ... [or] you're going to find yourself spending some quality time with your kids, in jail, together." Nutter believes much of the teen mob violence is a result of absentee fathers.