The US has been plagued by gun violence in schools for decades and now another sad chapter in that history has been written.
An 18-year-old gunman shot and killed 19 children and two teachers at an elementary school in Uvalde, Texas on Tuesday.
High school student Salvador Ramos is believed to have shot his grandmother before driving to Robb Elementary School and opening fire on children as young as seven-years-old. The gunman was shot dead by police officers at the scene.
One of the victims of the shooting was fourth-grade teacher Eva Mireles. Her grieving aunt said she was “furious that these shootings continue” adding: “These children are innocent. Rifles should not be easily available to all.”
The attack is the deadliest school shooting in America since Sandy Hook and the latest killings will inevitably reignite the debate in the US over tougher gun laws.
As with previous tragedies, investigators will be combing over Ramos’ history to try and explain what led to such a devastating loss of young lives.
Below we look at some of the killers behind the country’s most horrific school shootings - and the potential warning signs before they opened fire.
Adam Lanza: Sandy Hook Elementary School
Adam Lanza killed 20 children and six adults at an elementary school before turning the gun on himself in December 2012. The 20-year-old shot and killed his mother before the massacre at Sandy Hook in Newtown, Connecticut that US President Barack Obama described as “unconscionable evil”.
Born in Exeter, New Hampshire, Lanza was described by classmates as “deeply troubled.”
According to friends and family, he had also been diagnosed with Asperger's syndrome and was increasingly isolated in the run-up to the shooting.
In 2014 the FBI concluded in a behavioural analysis report there was “evidence to suggest the shooter had an interest in children that could be categorised as paedophilia”. But they found no evidence that he had acted on any potential sexual feelings toward children.
Olivia DeVivo was a student with Lanza in the 10th grade, at about the age of 15. She said he was “very shy and didn't make an effort to interact with anybody”.
He held National Rifle Association safety qualifications after visiting shooting ranges with his mother, Nancy.
In his online activity authorities uncovered his obsession with previous mass shootings and spree killings, including the 1999 Columbine High School shooting. Documents revealed Lanza had created a meticulous spreadsheet of previous mass murders.
He was not known to the police prior to the shooting further fueling the shock of the incident.
Eric Harris and Dylan Klebold: Columbine High School
The April 1999 Columbine high school shooting left 15 shot dead after 18-year-old Eric Harris and 17-year-old Dylan Klebold opened fire at the school in Colorado.
Harris was born in Wichita, Kansas,where he spent his early childhood before his family moved to Colorado as a teenager. He was described as a normal teen who played football but his diary entries revealed disturbing signs of a violent mind.
“I want to tear a throat out with my own teeth like a pop can,” he once wrote in his journal. “I want to grab some weak little freshman and just tear them apart like a f***ing wolf. Strangle them, squish their head, rip off their jaw, break their arms in half, show them who is God.”
Klebold was born in Colarado and was known as the more introverted of the pair. He grew up in a middle-class background home as the son of a geo-physicist. He had a relatively normal upbringing and also enjoyed sports and video games - however, like Harris he was dissatisfied with school .
Journals left behind by Harris and Klebold, investigators eventually discovered the teens had been planning for a year to bomb the school in an attack similar to the 1995 Oklahoma City bombing.
Investigative journalist Dave Cullen, author of the 2009 book Columbine, described Harris as “the callously brutal mastermind,” while Klebold was a “quivering depressive who journaled obsessively about love and attended the Columbine prom three days before opening fire.”
After the attack the pair killed themselves in the school library.
Ethan Crumbley - Oxford Michigan Shooting
Ethan Crumbley, 15, is accused of planning a mass shooting at Oxford High School that left four students dead and seven people injured.
It is alleged he carried out the massacre with a semi-automatic handgun bought for him by his parents on Black Friday as an early Christmas present.
Details emerged following the November 2021 shooting that the teenager posted disturbing social media posts in the run-up to the shooting. Journal entries, drawings and online searches also revealed a violent nature.
Crumbley had boasted on his Instagram page about a gun his father had purchased.
Just hours before the shooting, he wrote on Instagram: “Now I become death - destroyer of worlds - see you tomorrow Oxford.”
His journal also reportedly contains notes about his fantasies of committing violence toward his fellow students in his journal.
His mother, Jennifer Crumbley posted on Instagram showing a target practice with the caption “mother and son time”. The day before the shooting, his parents were contacted by the school after he was caught searching for ammunition during class.
School officials said the incident was escalated to school counsellors who were told by the teenager that he had gone to a shooting range with his mother Jennifer Crumbley that weekend.
She is said to have ignored the school’s attempts to reach out to her about the incident but reportedly texted her son at the time: “LOL I’m not made at you, you have to learn not to get caught.”
Nikolas Cruz - Stoneman Dougal High School
Cruz killed 14 students and three staff members on Valentine’s Day 2018, during a seven-minute rampage through a three-story building at Stoneman Douglas High School in Parkland, Florida.
One teacher said the former student had been flagged as a potential threat and he was a big enough concern that administrators had banned him from campus.
Cruz was expelled from school a year before the attack due to “disciplinary reasons.”
It later emerged that a YouTube user with the handle "nikolas cruz" left a comment on a Discovery UK documentary about the gunman in the 1966 University of Texas tower shooting. The user wrote beneath the YouTube video: “I am going to [do] what he did.”
Other past comments by YouTube users with Cruz's name reportedly included one remark in September, saying, “Im going to be a professional school shooter.”
An Instagram account belonging to “cruz_nikolas” was taken down shortly after the shooting. The account included photos of a young man wearing U.S. Army hats posing with guns and knives, his face mostly concealed.
A former classmate, Jillian Davis, said Cruz had a hot temper and a history of making dark, gun-related jokes.
Local police were criicised for apparnetly failing to following warning signs, including a record of threatening behaviour.
Cruz pleaded guilty to all charges last October and is due to be sentenced for his crimes in June.