Joe Biden vowed to “turn this pain into action” after meeting the grieving families of the Texas Elementary school shooting.
The USpresident spent three hours with relatives of the 19 schoolchildren and two teachers killed by gunman Salvador Ramos, 18, at Robb Elementary School in Uvalde.
It came at the end of a visit by the US president to the town on Sunday.
First Lady Jill Biden, herself a teacher, accompanied the president to a memorial of 21 white crosses - one for each of those killed before. Biden attended Mass at Sacred Heart Catholic Church, where several victims’ families are members, and one of the families was in attendance.
As Biden departed church to meet privately with family members, a crowd of about 100 people began chanting “do something.” Biden answered, “We will,”
Biden later tweeted: “To everyone impacted by the horrific elementary school shooting in Uvalde, Texas: We grieve with you. We pray with you. We stand with you. And we’re committed to turning this pain into action.”
The shooting on 24 May has provoked new calls for gun control measures.
The visit to Uvalde was Mr Biden’s second trip in as many weeks to console a community in loss after a mass shooting.
He travelled to Buffalo, New York, on May 17 to meet victims’ families after a gunman killed 10 black people at a supermarket.
Both shootings and their aftermath put a fresh spotlight on the nation’s entrenched divisions and its inability to forge consensus on actions to reduce gun violence.
“Evil came to that elementary school classroom in Texas, to that grocery store in New York, to far too many places where innocents have died,” Mr Biden said on Saturday in a commencement address at the University of Delaware.
“We have to stand stronger. We must stand stronger. We cannot outlaw tragedy, I know, but we can make America safer.”
Mr Biden also met first responders before the trip back to his home in Delaware. It was not clear if the group included officers who were involved in the immediate response to the shooting.
But several senior Republicans have already pushed back against calls for tighter rules on gun ownership, such as background checks, while on Friday, former President Donald Trump told the National Rifle Association’s annual conference that Americans should be allowed firearms to defend themselves against “evil”.
The US Department of Justice has said it will investigate the police response to the mass shooting.
Public anger is growing after it emerged that officers waited in the hallway as children trapped with the shooter made desperate 911 calls.
Announcing its Critical Incident Review on Sunday, the US Department of Justice said the goal was to “provide an independent account of law enforcement actions and responses that day, and to identify lessons learned and best practices to help first responders prepare for and respond to active shooter events”.
Officials said the commander believed the suspect was barricaded inside an adjoining classroom and that there was no longer an active attack.
The revelation caused more grief and raised new questions about whether lives were lost because officers did not act faster to stop the gunman, who was ultimately killed by Border Patrol tactical officers.
"It's easy to point fingers right now," said Ronnie Garza, a Uvalde County commissioner, before adding: "Our community needs to focus on healing right now."
Mckinzie Hinojosa, whose cousin Eliahana Torres was killed on Tuesday, said she respected Mr Biden's decision to mourn with the people of Uvalde.
"It's more than mourning," she said. "We want change. We want action. It continues to be something that happens over and over and over. A mass shooting happens. It's on the news. People cry. Then it's gone. Nobody cares. And then it happens again. And again.
"If there's anything if I could tell Joe Biden, as it is, just to respect our community while he's here, and I'm sure he will. But we need change. We need to do something about it."
Authorities have said the gunman legally purchased two guns not long before the school attack: an AR-style rifle on May 17 and a second rifle on May 20. He had just turned 18, permitting him to buy the weapons under federal law.
Hours after the shooting, Mr Biden delivered an impassioned plea for additional gun control legislation, asking: "When in God's name are we going to stand up to the gun lobby? Why are we willing to live with this carnage? Why do we keep letting this happen?"
