The jury has found Colin Gray, the man whose teenage son is accused of killing two students and two teachers in a shooting at Georgia's Apalachee High School, guilty of second-degree murder and all other charges.On Tuesday, after just a few hours of deliberating and two weeks of witness testimony, the jury announced that they had come to a verdict.Gray was charged with 29 counts, including second-degree murder, involuntary manslaughter, and cruelty to children. He had pleaded not guilty to all charges.His prosecution marks the third time a parent has been charged for their connection to a mass shooting allegedly carried out by their child, and the first adult charged in connection with a school shooting in Georgia.Gray's sentencing hearing has not been scheduled. He faces up to 30 years in prison for the second-degree murder charges.Four dead in Apalachee High School shootingInvestigators say on Sept.…