President Joe Biden has urged Americans to confront the country’s gun lobby and pressure Congress to tighten gun laws after a gunman murdered 19 children and two teachers in a U.S. school shooting.

“As a nation, we have to ask when in God’s name we’re going to stand up to the gun lobby when in God’s name we do what we all know in our gut needs to be done,” Mr Biden said in a televised speech.

Mr Biden, a Democrat, accused the gun lobby of blocking the enactment of stricter firearm safety laws. He ordered flags flown at half-staff daily until sunset on Saturday in observance of the tragedy.

“I am sick and tired of it. We have to act,” he said without going into specifics.

Authorities said Salvador Ramos, 18, on Tuesday shot his grandmother, who survived, before fleeing and crashing his car near Robb Elementary School in Uvalde, Texas, killing at least 21 people before he was killed, apparently by police.

Police cruisers and emergency vehicles were scattered around the perimeter of the school grounds. Uniformed personnel stood in small clusters, some in camouflage carrying semi-automatic weapons.

“My heart is broken today. We’re a small community, and we need your prayers to get us through this,” school district superintendent Hal Harrell told reporters with his voice quaking with emotion.

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 U.S. 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.

Mass shootings have frequently led to public protests and calls for stricter background checks on gun sales and other firearm controls common in other countries. Still, such measures repeatedly fail in the face of strong Republican-led opposition.

Democratic U.S. senator Chris Murphy of Connecticut, a leading advocate for legislation to restrict the proliferation of guns, told reporters, “I just don’t understand why people here think we’re powerless. There’s just not a coincidence that we’re the high-income world’s deadliest nation and we have the loosest gun laws.

He added, “You know, guns flow in this country like water. And that’s why we have mass shooting after mass shooting.”

(Reuters/NAN)