Hours after three brothers were seen playing with a gun outside their home, a 13-year-old Cobb County boy was dead Thursday night. A 16-year-old older brother is accused in death. But Friday afternoon, he was still on the loose. When he's found, the teen is expected to be charged as an adult and face felony murder and aggravated assault charges. Oscar Mondragon was often in trouble for having drugs or fighting, and bragged of having weapons, Sherly Parada, 15, told the AJC. Parada said Oscar, Javier and a younger brother were all playing with a gun outside earlier Thursday, hours before Javier was killed. A neighbor told the AJC she also saw the boys playing with guns, but assumed they were toys.