Salvador Ramos, 18, sent the haunting messages to a Californian woman he vaguely knew on Instagram saying “I got a lil secret I wanna tell u. I’m about to…” (sic) with a smiley face emoji covering its face. His message appeared to hint at his plans for the horrors he would inflict on a group of young school children and their teachers at Robb Elementary School in the town of Uvalde, Texas.
He also sent her a message just two hours before the shooting saying: “Ima air out”.
Ramos also tagged the woman in a highlighted post on his social media page, which showed pictures of guns.
The woman says the messages, which began on May 12, were completely random but she replied because she was scared.
He asked her from his account @sal8dor_: “You gonna repost my gun pics” to which she replied: “What your guns gotta do with me.”
But he quickly replied saying: “Just wanted to tag you.”
At 5.43am on Tuesday, @salv8dor_ messaged her on Instagram warning: “Im about to” which prompted the woman to query what he was talking about.
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The shooting unfolded around 11.32am.
The woman later posted on Instagram to express her horror at Ramos’s actions.
She wrote: “He’s a stranger I know nothing about him he decided to tag me in his gun post.
“I’m so sorry for the victims and their families I really don’t know what to say.“The only reason I responded to him was because I was afraid of him I wish I stayed awake to at least try to convince him to not commit his crime. I didn’t know.”
The 18-year-old, who was killed apparently by police, also had shot his own grandmother before fleeing from the scene, then crashing his getaway car and launching a bloody rampage at Robb Elementary School about 80 miles west of San Antonio.
His motive remains unclear.
Law enforcement officers saw the gunman, clad in body armour, emerge from his crashed vehicle carrying a rifle and “engaged” the suspect, who nevertheless managed to charge into the school and open fire, Texas Department of Public Safety (DPS) Sergeant Erick Estrada said.
A Texas DPS spokesperson later told CNN that 19 school children and two adults were killed, not counting the shooter.
The pupils would likely have ranged in age from 7 to 10-years-old.
University Hospital in San Antonio said on Twitter that it had received two patients from the shooting in Uvalde, a 66-year-old woman and a 10-year-old girl, both listed in critical condition.
Uvalde Memorial Hospital said 15 students from Robb Elementary were treated in its emergency room, with two transferred to San Antonio for further care, while a third patient transfer was pending. It was not immediately clear whether all of those students survived.
A 45-year-old victim grazed by a bullet was also hospitalised at Uvalde Memorial, the hospital said.
The rampage was the latest in a series of mass school shootings that periodically reignite a fierce debate between advocates of tighter gun controls and those who oppose any legislation that could compromise the right of Americans to bear arms guaranteed by the US Constitution.
It was the deadliest school shooting since a gunman killed 26 people, including 20 children, at Sandy Hook Elementary School in Connecticut in December 2012.