In other words, they aren't Christians, since they reject every aspect of Christianity.
"This people honors me only with lip-service, while their hearts are far from me. The worship they offer me is worthless; the doctrines they teach are only human regulations." (Matt.15:8-9).
"Make sure that no one traps you and deprives you of your freedom by some secondhand, empty, rational philosophy based on the principles of this world instead of on Christ." Colossians 2:6-8
Pretty much covers them.
I went to a Unitarian church once. I am not a religious person, but it struck me as completely devoid of any concept of God. It was just a bunch of liberals with nothing better to do on a Sunday morning.
I agree with everyone that this was a terrible act. But for those of you who do not want to drag religion into this, just wait. If the shooter is found to be a member of a Christian denomination, especially a conservative one, the MSM will instantly turn this into a direct attack by that denomination on the Unitarians.