The gunmen's name is Salvador Raimondo Ramos, age 18. He was a local in the community in which he murdered 22 people.
The 18-year-old, who died when police tried to arrest him, was a US citizen and a student in Uvalde, a small community near the Mexican border where the tragedy took place.
Ramos killed his grandmother first, before shooting up a school and causing 21 fatalities - 19 of whom were children, and 2 of whom were teachers.
Two officers were also shot, but survived the encounter.
This would make it the deadliest American school shooting since the massacre at Sandy Hook Elementary a decade ago.
The gunman was using two AR-15 - an assault rifle - variants, likely semi-automatic, because fully automatic weapons were banned federally.
The Washington Post, quoting one of his friends, said, "About a year ago, Ramos posted on social media photos of automatic rifles that 'he would have on his wish list'...Four days ago, he posted images of two rifles he referred to as 'my gun pics'".
Gunman posted images of the murder weapons to Instagram, before killing spree | Instagram
According to a report, Ramos's Instagram had one post, and sent a picture of two guns to a random Instagram user.
Ramos asked the Instagram user if he was reposting his "gun pics."
According to his direct messages, Ramos said he wanted to tell him a secret. The user followed the conversation until 1:16 pm.
He was reportedly killed by responding police.
Two parents, who said they were friends of the gunman's family, described him as serious and said he had a temper. One remembered he often talked back to his mother in his younger years. But both were surprised he could be capable of such violence., reported The New York Times.
Some media reports claimed that Ramos had a disturbed home life with frequent quarrels with his mother, who is allegedly a drug user. These reports could not be verified.
Months ago, Uvalde's Congressional representative Tony Gonzales, tweeted: "I voted no in two gun control measures in the House today. I am a proud supporter of the Second Amendment, and I will do everything I can to oppose gun grabs from the far left."
He was among a group of Republican lawmakers that approved Texans to carry handguns in public without a license and the background check and training.