 Grossman points out that there are great psychological costs that weigh heavily on the combat soldier or police officer who kills, if they are not mentally prepared for what may happen; if their actions (killing) are not supported by their commanders and/or peers; and if they are unable to justify their actions (or if no one else justifies the actions for them).The second edition of the book, along with an audio version, was released in 2009.Grossman claims in his book "On Killing" that soldiers are faced with four options once they have entered into combat.