Why Do Some People Kill Their Parents? An Expert Breaks Down 4 Types of Parricide Offenders (Exclusive) By Gillian Telling

Nick Reiner, 32, is charged with murder in the stabbing deaths of his parents Rob Reiner and Michele Singer Reiner. The double killing of one’s parents, known as parricide, is a rare event, according to Dr. Kathleen Heide, Ph.D., professor of criminology at the University of South Florida and author of Why Kids Kill Parents: Child Abuse and Adolescent Homicide.

“There are only about 250 parricide cases a year, and fewer than 20 of those are ‘double parricides,’ where both the mother and father are killed,” the expert tells PEOPLE. “Among those cases, most doing the killing are adults, or over 18,” she says. “And they are mostly male. Still, it’s a very, very rare event, which is a good thing.”

When it comes to a case like the Reiners, which Heide is not involved with, she says most people want to understand how such a terrible thing could happen.

“It really touches home. It creates a question of, ‘Could it happen to me?’ and that’s legitimate,” she says. “Parents, in most cases, are the people who love you the most. And in the case of Rob and Michele Reiner, what’s so horrifying is that we have every reason to believe that these were two loving, devoted, good parents. So when something this rare does happen, people tend to want to know, ‘What drove this?’ “

Heide says four types of children commit parricide.

The Abused Offender

“The first type is the severely abused offender,” Heide says.

“It’s usually a juvenile who is still living at home, where there is longstanding abuse — typically physical, maybe sexual, verbal abuse, and psychological abuse. There’s also almost always parental neglect. The motive is desperation; perhaps the person has tried other ways to get help, or maybe they’ve told a teacher or authorities. Or they’re so worried they’re going to be killed or a sibling will be killed. So that’s one type, and it definitely exists, more so with adolescents who feel trapped and don’t have criminal records. They are, quote unquote, ‘good kids.’ ”

The Mentally Ill Offender

The second type of offender, according to Heide, is severely mentally ill.

“These individuals have a longstanding history of mental illness, often schizophrenia or on the schizophrenia spectrum. Sometimes it’s bipolar disorder with psychotic features, but they’re typically on medication, and when the killing happens, it’s frequently because they’ve gone off their medication. So they have delusions. I’ve seen cases where they think God is commanding them to kill, or the devil is. They hear voices, they get signs. It’s not real, but they believe it is.”

Nick was reportedly taking medication for schizophrenia before the killing of his parents, according to the Los Angeles Times.

The Dangerously Antisocial Offender

The third type of person who commits parricide is “classified as dangerously antisocial,” Heide says.

“These are individuals who want to kill a parent to achieve a selfish, instrumental end. They may want their parents’ money. They may believe they’re being cut out of the will, or want their inheritance now. In some cases, females kill for love because their parents object to their boyfriend, and they want to be free to be in the relationship.”

She adds, “In these cases, these parents are obstacles. So they think, ‘Let’s remove the obstacle. Let’s get rid of the parent.’ They really think that will make everything fine. They’re not thinking about the repercussions.”

Heide adds that antisocial offenders often have a pattern of breaking the law or being oppositional.

“They’ve also usually been diagnosed as having antisocial personality disorder. They manipulate — and they’re good at it. They lie convincingly and often to get what they want. They’re grandiose and think they’re the best at whatever they do. They don’t take responsibility, and everything is everyone else’s fault. They usually want lots of money but won’t put in the effort.”

The Enraged Offender

The fourth type, she says, is the enraged offender.

“This is an individual who kills their parents because of conflict, and they’re in a state of rage,” she says.

“There are a number of pathways to that rage, and sometimes it’s abuse and neglect. But sometimes it’s because the parents have been overindulgent: They want to give their kids everything and always clean up their messes, but there comes a point when they tell the child it’s time to grow up and take care of themselves. These kids don’t have frustration tolerance. So it leads to rage. It’s almost like having a temper tantrum, but they’re big and strong.”

Related Stories

Rob and Michele Reiner Never Worried Son Nick Was Violent, Family Didn’t See ‘Anything Like This Coming’ (Exclusive Source)

Nick Reiner, Addiction and the Anguish and Fear of Modern Parenting (Exclusive)

Heide adds that none of the above can be determined quickly.

“You have to make sure to find out what drove the offender. You need to talk to them. You’re not going to find out what happened in a 30-minute interview. It’s always important to talk to surviving relatives to understand the household dynamics. Always get the long-term mental health, medical records, their struggles, and parental involvement. All those things are critical.”

As for parents who are worried it could happen to them, she says it’s important to take any threats of harm seriously. “I don’t care what age they are; if they say, ‘I’m going to kill you,’ it’s not an okay thing to say. Set boundaries. Get them evaluated.”

She adds, “Happy and healthy kids don’t kill their parents.”

Most of all, she says that every parricide case she’s ever evaluated or worked on is extremely sad.

“They’re all tragic,” she says. “The parents are gone, the family is forever changed, the alleged offender’s life is forever changed, and their friends are forever changed. The trauma extends to the community and everyone who knew and loved them.”