Certainly the greater environment that the Children have to live in has a major influence. Anyone that denies that is only looking at this problem from a one dimensional view. There is no way to completely block the Christianophobic rhetoric being splashed around the country in the media and in our schools.
From the other point of view, I know a minister's son who fits the profile of a Christianity reject and his experience was a both a combination of legalism and connections to all things secular. He eventually found more acceptance in the secular world. Even his parents have abandoned him. Sad.
The greater environment, as you put it, is too general a description of the anti-Christian movement. This anti-Christian movement is the center piece of the secular progressive agenda that is being spread across this country by the far left, hate America crowd. The anti-Christianity movement is based largely on the fundamentalist opposition to the homo-sexual life style, and I won’t be at all surprised if we find out that this shooter was gay. He may not have been, but that seems to be the most common basis for the leftist antipathy toward Christianity.