SAN DIEGO - A community is left stunned after the owner of a popular Santa Barbara surf school was charged Wednesday with killing his two young children with a spear gun in Mexico because he believed they would become monsters, authorities said.Matthew Taylor Coleman, 40, was arrested after the bodies of his 2-year-old son and 10-month-old daughter were found Monday morning by a farmworker at a ranch near Rosarito in Baja California, said Hiram Sanchez, Baja California’s attorney general.Coleman is facing a federal charge of the foreign murder of U.S.