Demonic influence, which God allowed, resulting in the murder of these persons.
This is the sad state of our corrupt nature that we humans do not treasure each other as created by God for His glory. Instead, our corruption acts selfishly...so much so that we continue to resemble Cain rather than Christ.
Luke 13:1-5
There were some present at that very time who told him about the Galileans whose blood Pilate had mingled with their sacrifices. And he answered them, “Do you think that these Galileans were worse sinners than all the other Galileans, because they suffered in this way? No, I tell you; but unless you repent, you will all likewise perish. Or those eighteen on whom the tower in Siloam fell and killed them: do you think that they were worse offenders than all the others who lived in Jerusalem? No, I tell you; but unless you repent, you will all likewise perish.”
The ultimate call is for all humanity to repent.
May God have mercy on the children and adults who were needlessly murdered.
May God take what is evil and turn it to reveal His goodness.