Here's what is a "trend": Zero police officers have been killed this year in New York and California, but there's been two each in Florida, Michigan, Texas, Alabama and Georgia. Last year, Georgia had five; Florida had three; Michigan had three; Texas and Alabama had just one.>Those are all "shall-issue" concealed carry states. That means you need a permit, but to get one, you just have to meet the requirements, not get approved.
Here's another and completely related "trend": zero officers were kiled in 2010 with knives. Zero were killed by bombs. One was killed with a car. All of the rest of the officers killed in 2010 were killed with guns: 38 with handguns, 15 with rifles, 2 with shotguns.