A violent incident in York County, Pennsylvania, has left three police officers dead and two others critically injured after they were ambushed while serving a warrant. The shooter, who reportedly stalked a residence in North Codorus Township before the attack, was identified and later killed by police. The rural community is in shock as details emerge, including that the gunman had concealed himself in a cornfield and opened fire with an AR-15. The FBI has joined local authorities in the investigation, and condolences are pouring in for the fallen officers and their families.