Should we try and understand a mass killer's mindset?

I understand that we don’t want to publicize and glamorize killers and there are many who emphasize how we should not hear anything from these people, let them fade into nonexistence. That might be pragmatic for the media, but what about for law enforcement and psychology? If we want to understand what motivates people to commit mass killings, we are going to have to try and get in their minds.