NINETEEN young children and two adults have died from a shooting at Robb Elementary School in the city of Uvalde, South Texas, United States (US), after a teenager armed with a handgun, an AR-15 semi-automatic rifle and high-capacity magazines opened fire, investigators said.

Acting alone, the 18-year-old suspect reportedly gained entry into predominantly Hispanic school with nearly 500 enrolled pupils aged seven to 10, and started shooting at 11:32am local time on Tuesday, before he was killed by law enforcement agents.

The Associated Press (AP) news agency reports that a US Border Patrol official who was nearby when the shooting began rushed into the school and shot and killed the gunman, who was behind a barricade.

The Uvalde Memorial Hospital posted on Facebook earlier that 13 children had been taken to hospital “via ambulances or buses”. However, the death toll from Tuesday’s shooting continues to mount and it is already the second-deadliest shooting at an elementary, middle or high school on record in the US.

“As a nation, we have to ask when in God’s name are we going to stand up to the gun lobby? When in God’s name will we do what we all know in our gut needs to be done? It’s time to turn this pain into action for every parent, for every citizen of this country,” US President Joe Biden said, his voice heavy with emotion.

A policeman talks to people asking for information outside of the Robb Elementary School in Uvalde, on May 24. Dario Lopez-Mills—AP

Texas Governor Greg Abbott said the shooter, later identified as Salvador Ramos, abandoned a vehicle before entering the school to “horrifically, incomprehensibly” open fire.

Texas Department of Public Safety officials told CNN Ramos who was wearing a body armour, was believed to have shot his grandmother before heading to the Elementary School.

Family members have continued to confirm the deaths of their loved ones. Lisa Garza, of Arlington, Texas, mourned the death of her cousin, Xavier Javier Lopez, who had been eagerly awaiting a summer of swimming, while Angel Garza said on Facebook that his daughter Amerie had been killed.

“My little love is now flying high with the angels above. Please don’t take a second for granted. Hug your family. Tell them you love them,” Garza said.

One of the adults killed was a teacher named in US media as Eva Mireles. Her page on the school district’s website said she has a daughter in college and loved running and hiking.

United Nations Secretary-General António Guterres said he was “deeply saddened by the heinous mass shooting” at the elementary school.

“It is particularly heart-wrenching that most of the victims are children. My heart goes out to the families and loved ones of the victims and to the community of Uvalde,” he said.

Reiterating Biden’s position, former United States secretary of state and presidential aspirant Hilary Clinton, said thoughts and prayers are not enough.

“After years of nothing else, we are becoming a nation of anguished screams. We simply need legislators willing to stop the scourge of gun violence in America that is murdering our children,” she said.