In rare cases, they do it because of a provocation. However, unlike predatory animals who kill other animals to satisfy their hunger, serial killers don’t have a legitimate need and usually kill just because of the heck of it.
Just like how a carnivore locks in on its target, serial killers often display the same calm and purposeful behavior.
For instance, a serial killer who happened to be a doctor, Harold Shipman, abused his position as a medical expert to make his patients opt for treatments that ultimately led to their death. They are also extremely skilled in manipulating a situation to try to appear innocent and often use trending news or medical psychological studies to back up their claims and justify their actions. Some of the best known serial killers in the world were very manipulative and knew exactly how to get their way. In order to hide their sinister personality, serial killers try to come off as vulnerable and show as if they have a need to please. Some serial killers have also been known to collect, dissect, and dismember animals as kids. Since serial killers murder others to have an illusion of controlling other lives, kids get that sense of control by killing small animals. Kids who find pleasure in killing or torturing small animals such as birds, squirrels, and cats and have no remorse afterward often turn out to be sociopaths. This could be one of the strongest warning signs and should not be taken lightly. For instance, they would often hide the bodies of victims from the police in a bid to assert control and power. To exert control over others, they sometimes withhold information to gain attention, exhibit a sense of authority, or to have the upper hand during a situation. Serial killers are attracted to power, and they like to have some semblance of control even after they have been caught and the ball is no longer in their court. Some other red flags include regression from very social to extremely anti-social.
However, this is not a definitive sign, not everyone who is antisocial is a serial killer. Serial killers are usually psychopaths, and their behavior is often antisocial.