DES MOINES, Iowa—Authorities arrested six teenagers accused of shooting into a group that had gathered outside an Iowa high school, killing a 15-year-old boy and seriously wounding two teenage girls, police said Tuesday. The suspects are each charged with first-degree murder and two counts of attempted murder in the Monday afternoon shooting on the grounds of East High School, near Des Moines’ downtown, about a half-mile from the Capitol. Police said gunshots fired outside the school came from several shooters from multiple vehicles. Police named the suspects as Octavio Lopez, 17; Henry Valladares-Amaya, 17; Manuel Buezo, 16; Romero Perdomo, 16; Alex Perdomo, 15; and Nyang Chamdual, 14. All are from Des Moines and the school district didn’t identify any as attending East. Police identified the 15-year-old killed as Jose David Lopez, of Des Moines. Lopez, who was not a student at the school, was the intended target of the drive-by …