AI does not react to bodies unless you script it. In my mission Defensive Strike there are static guards and some patrols. I have a script that checks to see if the static guard is not alive and getPos select 2 < -0.5 (ie is it underground) and distance from a partol less than some small value 20 or so. If the conditions are met (not alive, distance to patrol < 20 and getPos select 2 < -0.5) then an alarm is raised.
Note that hiding a body first puts it under ground (getPos select 2 goes to about -1 I think) and then after about a minute it gets moved a very long way away.