*Warning: the following article contains details of murder that some readers may find upsetting. The accuracy of the claims cannot be independently verified.

Reddit users have gathered together online to reveal their startling personal connections to some of the world's most notorious and prolific murderers or serial killers.

If taken as read, the anecdotal discussion - which cannot be confirmed - could provide a useful and revealing insight into the emotional aftershock experienced by the families and friends of those who kill.

Titled: 'People who have known murderers, serial killers, etc. How did you react when you found out? How did it effect [sic] your life afterwards?', the thread has had more than 6,000 responses.

Some mention the infamous kidnapper and rapist Ted Bundy, Colorado movie theatre gunman James Holmes and 'American Sniper' killer Eddie Ray Routh, while others talk of childhood friends or classmates who are arguably less well-known, but were once at the centre - or cause - of similar tragedy.

One comment, which is rated top of the thread, details the murder of a girl by his sister's ex-boyfriend.

"My sisters ex-boyfriend is in jail currently for killing his next girlfriend and putting her body into a cement-sealed barrel," he writes, astoundingly.

"It's so awful for that girl and her family, but all I could think is what a sucidal revenge mission I would be on if it had happened to my sister. It still keeps me up at night."

Another user claims to have known the Colorado movie massacre gunman James Holmes, 27, who killed 12 people and injured 70 others in 2012.

He was convicted of first-degree murder and 140 counts of attempted first degree murder for the shooting at a packed midnight screening of a Batman film at a multiplex in the Denver suburb of Aurora.

Police found a weapons arsenal at the home of James Holmes

The Reddit contributor says that she knew Holmes - who was handed life sentences for each fatality and given a maximum 3, 318 years in prison - in college.

"I remember him being super paranoid," she writes. "I remember filling out health questionnaires/medical clearance forms for a final that required in vivo work and access to the vivarium.

"He threw a fit in our lab, telling our TA he wasn't going to fill it out. He finally did, but put a disclaimer on the bottom of it. It was bizarre. I think that was around 08/09, I think he was already unraveling then."

She also says that she remembers the moment she first found out what had happened in Aurora. "I was working when my old college roommate text me asking if I heard about the shooting in Colorado followed shortly by her texting me who did it.

"I remember feeling scared for some reason when I put the name to a face. My teeth started chattering wildly. I was shocked.

"It still freaks me out to this day remembering working in labs, and having class discussions with that guy.

"We were definitely not friends but, I probably saw him nearly every day for at least a couple years. I can still see him working across from me under a fume hood in my minds eye anytime his name is brought up."

He never seemed to make eye contact with anyone <p>A Reddit user recalls going to college with James Holmes</p>

The comments in response to her post are just as interesting - and contain similarly personal links to the tragedy.

One Redditor says: "One of my classmates was shot in the head at that shooting. It's interesting to hear from someone who knew him before that time."

To which the original poster adds: "The only other thing that I remember was that he never seemed to make eye contact with anyone. Totally thought that was just an introvert thing, but still odd."

And others have comparable links to some of the world's most notorious criminals - including Ted Bundy, the prolific serial killer who confessed to murdering at least 30 young women in the 1970s, including 12-year-old Kimberly Leach.

Ted Bundy's 12 year old victim Kimberly Leach (AFP/Getty)

"Ted Bundy dated my aunt," one person writes, astonishingly. "I grew up in Kirkland, Washington - which is right outside of Seattle. My aunt lived in Ballard at the time.

"They dated for a few months and it just sort of fell apart. She said that he was one of the most polite, nicest people that she had ever met."

The author's post prompts an outpouring of anecdotes.

"When Ted Bundy was in prison (in Florida, I think?) his favorite reporter to speak with was my cousin," one writes. "She still has the Christmas card he sent her one year."

But, the user adds: "They had a falling out while he was on death row, and I think he sent her death threats."

Bundy's case, which was documented in an eponymous film directed and co-written by Matthew Bright in 2002, is not the only one of its kind to have been immortalised on screen in recent years.

One Redditor describes being deployed with former US Marine Eddie Ray Routh - subject of the film 'American Sniper'.

He was found guilty and sentenced to life in prison without parole in February for shooting and killing soldier Chris Kyle and his friend, Chad Littlefield, at a Texas gun range in 2013.

Lawyers for Eddie Ray Routh have said he was insane and is not guilty of murder (Reuters)

"I deployed with Eddie Ray Routh, who later went on to kill Chris Kyle (AKA American Sniper)," he writes.

"The talk about him made me abundantly aware of the fact that all veterans have a tough time getting help with their mental health after we come back.

"Combat veterans face social pressure to "man up," but noncombat veterans get that plus accusations that they're lying because people think only combat can cause PTSD."

The soldier, while not excusing what Routh did, goes on to describe the kind of trauma experienced by veterans in places like Haiti, to which end, he says, he "still can't eat mango without running the risk of uncontrollably sobbing because the taste instantly reminds me of what it was like". Routh, he claims, was there with him.

"One bite, and I feel the humidity," he writes evocatively. "I smell the burning garbage and the pig s**t from the two feral pigs that we accidentally fenced into our camp.

"I see refugee camps with people living in tents made of their own clothes, holding signs that say "America Help".

"I'm THERE again, and I never saw combat. But try telling that to 90% of post-9/11 veterans, and the response is "Bulls**t you f*****g pussy, you didn't even go to Iraq.""

Routh was there in Haiti with me <p>Unidentified US soldier recalls being deployed overseas with Eddie Ray Routh</p>

Others recall chilling connections to killers in their childhoods - before they went on to commit heinous acts of violence.

"In grade school I sat next to this guy named George," someone writes. "Super quiet kid, and occasionally I would go over his house after school. His mom would occasionally be our substitute teacher.

"Fast forward to when I am in college and go to pick up a NY Post in the morning. I see the headline "THREE STRIKES, SHE'S OUT ... KID BEATS MOM TO DEATH WITH BASEBALL BAT". And there was a photo of George and his mom."

The Healthcare Serial Killers dubbed the 'Angels of death' Show all 5 1 /5 The Healthcare Serial Killers dubbed the 'Angels of death' The Healthcare Serial Killers dubbed the 'Angels of death' Colin Norris Colin Norris used insulin to kill patients, targeting frail elderly women in 2002 while working at two Leeds hospitals. He was jailed for life in March 2008, when he was 32, after he was found guilty of four counts of murder along with attempting to kill another woman at Leeds General Infirmary and the city's St James's Hospital. Detectives said he showed no remorse and he has always protested his innocence and denied injecting patients with insulin. PA The Healthcare Serial Killers dubbed the 'Angels of death' Benjamin Green In 2006 Geen, who was then 25, was given 17 life sentences after he was found guilty of murdering two of his patients and attacking 15 others. His trial heard that Geen gave them injections of drugs such as muscle relaxants, insulin and sedatives to stop them breathing while working at the Horton Hospital in Banbury, Oxfordshire. The court also heard of his thrill at attempting to revive these patients. pa The Healthcare Serial Killers dubbed the 'Angels of death' Anne Grigg-Booth The 52-year-old was found dead at home after taking a drug overdose in 2005, eight months before she was due to go on trial accused of murdering three elderly women at Airedale General Hospital, near Keighley, and the attempted murder of a middle-aged man. She had worked at the hospital for 25 years and was also facing 13 counts of unlawfully administering poison to 12 other patients. The charges related to her injecting patients with high doses of painkilling drugs such as morphine and diamorphine while she worked on the night shift. PA The Healthcare Serial Killers dubbed the 'Angels of death' Harold Shipman Dr Harold Shipman, one of the most prolific serial killers the UK has known, was convicted at Preston Crown Court in 2000 of the murder of 15 of his patients while he was a general practitioner in Hyde, near Manchester. Police also investigated allegations that he might have murdered many more patients while he was working in Hyde, Todmorden and Pontefract. A major inquiry into his activities concluded the doctor killed about 250 patients between 1971 and 1998. PA The Healthcare Serial Killers dubbed the 'Angels of death' Victorino Chua Victorino Chua was found guilty of murdering two patients and poisoning 19 others at the Stepping Hill hospital in Stockport. He killed and poisoned his victims using insulin. He wrote a 13-page letter discovered by police that stated: "They thought I'm a nice person but there a devil in me. I know if I go, I go straight to hell no question ask." Rex Features

Some reveal how they cannot even begin to understand what motivates people they once knew to 'snap'.

"I went to school with a popular guy, on the pro athlete team, but always kept to himself," a Redditor says. "He seemed to only interact with others when he was playing with his teammates. But he wasn't awkwardly quiet or anything.

"But then he was on the news for killing his gf, gf's mom, and little sister (minor). Police found him walking down the street with blood all over him.

"It just seems weird because you know this person and it makes you wonder what made them react to that extent."

You wonder what made them react to that extent <p>A contributor recalls going to school with someone who went on to murder his girlfriend and her family</p>

And there are even some users who talk about deaths as family legend.

"One day I was working on a family tree, and I'm quizzing my mom about different names and connections and stuff," a user writes.

"Then out of nowhere she tosses out, "And then there was old Aunt Tillie, who strangled a little boy in her living room."

Another says: "I found when I was like 13 that both my grandfather and uncle had killed. I never met either of them.

"My uncle killed 2 people. The first one he stabbed a guy like 80 times, slit his throat ear to ear and then cut him from b***s to throat.

"He wrote on the walls with the guys blood, kinda Charles Manson like. The second person was a woman he met at the bar. He stabbed her around 70 times and dismembered her."

Others describe what it's like to work with people who have committed murder.

"I'm a forensic psychologist and work at a state hospital on the unit for people found Not Guilty by Reason of Insanity," one of the posters on the thread says.

"Many of the clients' index offenses are murder or attempted murder. Because of the circumstances of their crimes they are usually in the paper with varying degrees of follow-up media attention.

"When new staff first transition to the unit they are shocked at how generally stable most of the clients are.