A gunman massacred 19 children on Wednesday at an elementary school in Texas, marking the bloodiest school shooting in the United States since the 2012 attack on Sandy Hook Elementary School in Newtown, Connecticut.

According to Lt. Chris Olivarez of the Texas Department of Public Safety, the 18-year-old gunman wore body armor and fired hundreds of rounds, killing 19 students and two teachers.

A senior Department of Homeland Security official informed USA TODAY that one of the U.S. Border Protection agents who responded to the scene shot and killed the gunman.

At approximately 11:30 a.m. Central Time, the assailant entered Robb Elementary School in Uvalde, Texas, and began unleashing a salvo of fifire, according to Texas Governor Greg Abbott Gov.

The death toll is expected to grow, federal law enforcement sources who spoke to the Associated Press, said. They talked under the condition of anonymity because they were not authorized to discuss investigational details.

Hal Harrell, superintendent of the school system, said at a news conference that grief counselors would be available and classes would be canceled for the remainder of the year, describing the incident as tragic and senseless.

Abbott said that two responding officers were wounded by gunshots but were not critically hurt.

Officials have not disclosed a motive for the shooting, but they have identified the perpetrator as a local citizen. Salvador Ramos was recognized as the shooter by Abbott.

Pete Arredondo, chief of police for the Uvalde Consolidated Independent School District, said at a press conference that the shooter acted alone.

Uvalde, located 85 miles west of San Antonio, has a population of roughly 16,000 people. Four years ago, a gunman opened fire at Santa Fe High School in the Houston region, killing 10 people.

"To lose a child is like having a piece of your soul ripped away," President Joe Biden said, during a Tuesday night news conference.

"Why are we willing to accept this killings?" he said. "The time has come to act on this suffering."

The agent who killed the gunman was assigned to a local unit inside Customs and Border Protection's special operations division, BORTAC or Border Control Tactical Unit, according to a U.S. homeland security official who spoke on condition of anonymity to discuss an ongoing investigation.

The agent was shot in the foot or lower leg when engaging the gunman, a DHS official said. He was treated at a local hospital.