TUCSON, AZ (KPHO/AP) - Davis-Monthan Air Force Base has stepped up security and limited traffic in and out of the base in the midst of reported gunfire. A Davis-Monthan Air Force Base spokesperson could not confirm reports of gunfire or say if anyone has been shot. An elementary school on the base is on lockdown, but a spokeswoman would release few details other than no one was being allowed in or out of the base