He might have not known that, but the result will be the same. He wanted to insult her. Pure evil.
I have heard/read this also.
But, with the kindergarten kids - he shot the multiple times each - reportedly 3 to 11 times each. Overkill - VERY personal and very punishing to the survivors (the families of the children? Why?)
Another mob story I've heard/read is that you don't kill your mark - you kill family, friends, anyone dear to the mark, so that the person, your mark, suffers for the rest of their lives.