Compassion isn't a bowl of sugar that runs out. We don't have to choose to have compassion either for the victims or the mother. We can have both.
The whole nature of radicalisation is that the extreme becomes the normal. It's insidious. Nobody starts the journey to radicalisation thinking 'yeah I want to be a murderer!' They are targeted for their vulnerability. It's no surprise that he grew up in less than ideal circumstances. He was groomed - they all are.
Why is it that we accept that young people can be groomed to form sexual relationships that they otherwise wouldn't consider, we can accept that some vulnerable women can be groomed to perform awful acts against their children by a paedophile, we can accept that some women can be groomed to accept terrible DV as if it is just what they deserve in life, but we can't accept that some young people can be groomed to perform acts that they would otherwise have found to be abhorrent?
This is evil in action and I don't believe that, by the time they actually do the attack, many of these radicalised young people are 'free agents'. They are ensnared both physically and mentally. Yes, they may have had some choices in the very early days and they may have made some mistakes, but they were never free agents. They were chosen because they fit a profile. They were chosen for their vulnerability and exploited.