UVALDE, May 26 —Two days after a teenage gunman murdered 19 children and two teachers inside a South Texas elementary school classroom, many details surrounding the massacre remained murky, as the small town of Uvalde reeled from the deadliest school shooting in nearly a decade.

A spokesperson for the Texas Department of Public Safety, Chris Olivarez, said today that investigators were still trying to confirm a precise timeline, including how long the gunman, 18-year-old Salvador Ramos, remained barricaded before officers breached the classroom and killed him.

The shooting has reignited a national debate over the country's gun laws. President Joe Biden and his fellow Democrats have vowed to push for new restrictions, despite resistance from Republicans.

There were few warning signs: Ramos, a high school dropout, had no criminal record or history of mental illness. Governor Greg Abbott said on Wednesday that Ramos had written an online message to someone minutes before the attack saying he was about to "shoot up an elementary school."

Authorities said Ramos shot his grandmother in the face at the home they shared before fleeing and crashing his car outside Robb Elementary School sometime around 11:30 a.m. (1630 GMT). His grandmother, who is hospitalized in critical condition, managed to call police.

Outside the school, Ramos, armed with an AR-15 semi-automatic rifle, evaded a school police officer, dropping a bag full of ammunition as he did so. Officials have offered conflicting accounts as to whether Ramos and the officer exchanged gunfire before Ramos was able to enter the school.

"We're trying to establish exactly what was his role and how he encountered the shooter," Olivarez told CNN.

Ramos wounded two responding officers inside a hallway before barricading himself inside a fourth-grade classroom, Olivarez said. The attack drew a massive law enforcement response, including hundreds of officers, who encircled the building and broke windows in an effort to evacuate children and staff.

Police set up a perimeter to prevent people, including parents, from trying to enter the school, Olivarez said. Eventually, members of a US Border Patrol tactical unit breached the classroom and apparently killed Ramos, with one agent wounded in the crossfire, officials said.

The Uvalde Police Department announced the incident was over shortly after 1 p.m. (1800 GMT).

Olivarez said the attack lasted between 40 and 60 minutes, though he could not say whether that time frame began when Ramos shot his grandmother or when the teenager arrived at the school. The FBI is working on obtaining surveillance video from the school's cameras.

Ramos purchased two semi-automatic rifles and hundreds of rounds of ammunition in the days leading up to the attack.

The suspect's mother, Adriana Reyes, was quoted in an interview with the British-based news site DailyMail.com describing her son as someone who "kept to himself and didn't have many friends."

At least 17 people were also injured, including multiple children.

Victims' loved ones took to social media to express anguish over the loss of children who never came home from school.

"We told her we loved her and would pick her up after school," Kimberly Mata-Rubio posted on Facebook in a remembrance of her daughter, Alexandria Aniyah Rubio, a fourth-grade honor student. "We had no idea this was goodbye."

Gun control debate

The shooting came 10 days after an avowed white supremacist shot 13 people at a supermarket in a mostly Black neighborhood in Buffalo, New York.

In Washington, Democrats and Republicans in the Senate appeared far from any compromise on new gun restrictions.

Biden, who has urged Congress to act, will visit Uvalde in the coming days.

The National Rifle Association's annual meeting starts tomorrow in Houston, where Republicans including Abbott, US Senator Ted Cruz of Texas and former President Donald Trump were scheduled to address the gun rights group.

The NRA expressed sympathy for the victims but said the event would go on as planned.

Shootings have become so commonplace in American schools that data shows a gun being fired almost every day this year on school property, according to the Naval Postgraduate School's Center for Homeland Defence and Security.

The Texas rampage is the deadliest U.S. school shooting since a gunman killed 26 people, including 20 children, at Sandy Hook Elementary School in Connecticut in December 2012. Like that one, the Texas attack left parents across the country fearful and grieving.

Uvalde is a close-knit community of about 16,000 residents, nearly 80% of them Hispanic or Latino, according to US Census data. The town's small size ensured that many residents personally knew some victims, or their families, including the town official faced with the grim task of identifying the bodies.

By last evening, the elementary school remained cordoned off with crime-scene tape, as passers-by walked up periodically to hand off flowers and stuffed animals to a police officer who carried it over to a makeshift memorial near the building. — Reuters