As we don't have the actual facts about the 'gilbert killing three kids story', we can only hypothesize about motives. It might be that Gilbert was in a desperate situation in his own life and took out his frustration on the innocent kids. Or there could be some sort of delusion in his mind that made him think harming the kids was necessary. Without proper details, we can't be certain at all.
Since I don't know the details of this story, it's hard to say the motives. It could be due to mental illness, or some personal grudges against the families of the kids. But this is just speculation without more information.
Not having the full story makes it tough to determine motives. However, in general, motives for such a heinous act could range from a desire for revenge, perhaps if Gilbert felt wronged by someone related to the kids. Another possibility could be some form of psychological breakdown where he was unable to control his violent impulses. But again, this is all just guesswork.
There are unfortunately many stories of violence in the world. If this 'gilbert killing three kids story' is a real event, it must be a tragic and horrifying one. But since I have no information about it, it's impossible to provide more details. It might be a story from a particular community, or it could be something that was reported in a very limited scope.
Mental illness. Just like anywhere else, small towns can have individuals with mental health issues that may lead them to commit a killing, perhaps due to hallucinations or uncontrollable impulses.
It could be that she was lonely. Living alone in that house, she saw the kids as a way to have some company, though her way of inviting them was very wrong and dangerous.
Jealousy could be one motive. They might be jealous of Harry's special status as a wizard. They see him as different and a threat to their 'normal' family life, so they want to get rid of him.
One possible theme could be love against all odds. Maybe they faced family opposition or social barriers.
One possible motive could be Anakin's fall to the dark side. The dark side clouds his judgment and makes him see Obi - Wan as an obstacle to his power. He might believe that by eliminating Obi - Wan, he can fully embrace the dark side and gain more control. Another motive could be jealousy. If Anakin feels that Obi - Wan is always favored or is holding him back in some way, this could fuel his anger and lead to him wanting to kill Obi - Wan. Also, the influence of Palpatine might play a huge role. Palpatine could have manipulated Anakin into believing that Obi - Wan is a threat to the new order he wants to create.
One possible motive could be a conflict over their loyalties. Remus is a werewolf and has his own set of insecurities and allegiances. Maybe Snape discovers something about Remus that he threatens to expose, leading Remus to kill him in a moment of panic. For example, if Snape were to find out about Remus endangering students during his werewolf transformations and was about to report him to the authorities.
In the 'babynapped real story', motives can be complex. There could be cases where the kidnapper has some sort of vendetta against the family. Maybe they want to cause the family emotional pain. Also, in some rare instances, the kidnapper might be involved in illegal adoption rings where they abduct babies to sell them to people who are desperate to adopt.
One possible motive could be ransom. The kidnappers may think the girl's family is wealthy and they can get a large sum of money in exchange for her safe return.
One possible motive could be a desire for revenge. For example, if a parent loses custody in a divorce, they might abduct the child out of anger towards the other parent. Another motive could be financial, like in the case where a family member abducts a child hoping to get a ransom from a wealthy family.