A 16-year veteran of the Phoenix Fire Department collapsed and died while on duty Monday afternoon, fire officials say. Division Chief Mike Sandulak said fire engineer Mark Carter came on duty at 8 a.m. and he and his crew worked several medical emergency calls and had stopped to get lunch when he was stricken, Sandulak said. Fire officials said they believe Carter suffered some sort of medical condition. Efforts by fellow firefighters to revive him were unsuccessful, the department said. Officials said they are awaiting a report from the medical examiner's office to determine the exact cause of death. In the meantime, officials said they are in the process of conducting an internal review.