For the answers we need only look to Islamic doctrine.
First of all, Jihadists have stated repeatedly that they do not regard kafir civilians as “innocent.” Here it is stated in no uncertain terms by the Islamic State in a release from September 2014:
Kill the disbeliever whether he is civilian or military, for they have the same ruling. Both of them are disbelievers. Both of them are considered to be waging war (the civilian by belonging to a state waging war against the Muslims). Both of their blood and wealth is legal for you to destroy, for blood does not become illegal or legal to spill by the clothes being worn.
The greater question, of course is, how could they leave behind a baby girl and family members to perform such an act, even if they believed it was justified?
When Muslims die they don’t believe that they will go straight to paradise. They believe that they must endure the “torments of the grave” until judgment day. The “torments of the grave” is positively gruesome. Muslims believe that they will be able to feel all of the decomposition and associated effects while they are in the grave.
There are exceptions, however.
Those who die while waging Jihad for Allah believe that they will not have to endure the torments of the grave, but will go straight to paradise, with all of its wonderful benefits. Such people are called shahids.
Not only that — and this is the most important point — shahids also win passage for some 70 family members when they die waging Jihad for Allah.
So, Syef Farook and Tashfeen Malik believed that they were doing something great for their baby daughter and their families by waging Jihad and dying in that cause. By what they believe, they all, including the baby, have thus been earned a trip to paradise without having to endure the torments of the grave.
This is Islamic doctrine and it explains the actions of the numerous Muslims who have joined the global Jihadist movement.
This article was written by Christopher W. Holton and published in Terror Trends Bulletin here.