Authorities said a gunman killed 19 children and two teachers at a Texas elementary school Tuesday, the state’s deadliest shooting in modern history and the country’s third mass shooting within weeks.

An 18-year-old male, armed with a rifle, shot his grandmother before driving to Robb Elementary School in Uvalde and overpowering a school officer, according to Texas Department of Public Safety Sgt. Erick Estrada.

What followed was the deadliest shooting at a U.S. grade school since the 2012 attack at Sandy Hook Elementary School in Newtown, Connecticut.

Families waited into the night, holding prayer circles and providing DNA samples to authorities in hopes their children were alive. Public officials across the country expressed outrage and sadness following the attack. 

More developments:

►Federal law enforcement officials told the Associated Press that the death toll was expected to rise. They spoke on condition of anonymity because they were not authorized to release investigative details.

►Officials have not identified a motive in the shooting, but the gunman appeared to have acted alone, Uvalde Consolidated Independent School District Chief of Police Pete Arredondo said at a news conference.

‘CONSTANT FEAR’:It’s not just Uvalde, Texas — gunfire on school grounds is at historic highs in the US

Where did the shooting take place?

Authorities say the gunman walked into Robb Elementary School in Uvalde, Texas, about 85 miles west of San Antonio, around 11:30 a.m. Central time and opened fire. Uvalde is home to about 16,000 people and is located about 75 miles from the Mexican border. About 82% of the city’s population is Latino, according to the U.S. Census Bureau. 

Robb Elementary, part of the Uvalde Consolidated Independent School District, has an enrollment of just under 600 students. The district initially put all campuses on lockdown after gunshots were fired, and it canceled all district and campus activities, after-school programs and events.

What do we know about the victims?

Nineteen children and two teachers were killed in the shooting, Texas Department of Public Safety Lt. Chris Olivarez said. A U.S. Border Protection agent, one of several responding to the scene, shot and killed the gunman, a senior Department of Homeland Security official told USA TODAY on Tuesday night.

University Health, a hospital in San Antonio, reported on Tuesday evening that they have four patients: a 66-year-old woman in critical condition; a 10-year-old girl in critical condition; a 10-year-old girl in good condition, and a 9-year-old girl in good condition. By nightfall, many families were still waiting for updates, hoping to hear that their children were in a hospital in Uvalde or San Antonio.

BLOODSHED SINCE SANDY HOOK:Uvalde school shooting among deadliest school attacks in past 10 years

Public officials react to the shooting

President Joe Biden in a Tuesday night news conference decried “another massacre” that had left parents in unfathomable pain: “To lose a child is like having a piece of your soul ripped away,” he said. Biden also called for a renewed push for gun control measures, lamenting the lack of progress despite repeated shootings.