Two out of every three law enforcement officers who were killed in 2011 were wearing body armor, according to preliminary data released by the FBI today.

Of the 72 victim officers, 49 were wearing body armor at the times of their deaths, according to the FBI. The data was released as a preview of the FBI's annual "Law Enforcement Officers Killed and Assaulted" report, which arrives in the fall.

In 2011, 72 officers were feloniously killed in the line of duty. That number was 16 more than the 56 officers slain in 2010.

Of these 72 deaths, 19 officers were killed during ambushes (14 during unprovoked attacks and five due to entrapment situations); five were slain while investigating suspicious persons or circumstances; 11 were killed during traffic pursuits or stops; five of the fallen officers interrupted robberies in progress or were pursuing robbery suspects; and four died while responding to disturbance calls.

Six officers died during tactical situations; one died while conducting investigative activity; one officer died while handling or transporting a prisoner; and 20 officers were killed while attempting other arrests.

Offenders used firearms in 63 of the 72 deaths. By type of firearm, 50 officers were killed with handguns; seven with rifles; and six with shotguns. Criminals used vehicles to kill six officers; weapons such as hands, fists, and feet to kill two officers; and a knife or cutting instrument to kill one officer.

Seventeen of the victim officers fired their own weapons, and four were killed with their own weapons. Ten officers attempted to use their own weapons. Seven of the slain officers had their service weapons stolen.

There were 68 separate incidents that resulted in the deaths of 72 officers. Of those incidents, 67 were cleared by arrest or exceptional means.

By region, 29 victims were killed in the South, 21 in the Midwest, 10 each were killed in the West and the Northeast, and two were killed in Puerto Rico.

In addition to the officers who were feloniously killed in 2011, 50 officers were killed in accidents. This is a decrease of 22 officers compared with the 72 officers who were accidentally killed in 2010.