People in the city of Uvalde in the southern US state of Texas have mourned the deaths of 21 victims of a school shooting.

In a memorial on Wednesday at an arena near the site of the shooting, people offered prayers for the 19 elementary school students and two teachers who were shot to death on the previous day. Some of the mourners carried photos of the young victims.

The shooter, 18-year-old local high school student Salvador Ramos, stormed the elementary school on Tuesday and started firing. He was shot dead by a law enforcement officer at the scene.

Texas Governor Greg Abbott told a news conference on Wednesday that Ramos had posted on Facebook that he shot his grandmother and was going to shoot people at an elementary school.

But a spokesperson for Meta, which operates Facebook, said the governor was inaccurately referring to what the company said were private messages.

Local law enforcement officials have confirmed that Ramos fired at his grandmother before driving to the school, and that she sustained severe injuries.

The Associated Press and other media said Ramos bought at least two assault rifles and ammunition this month shortly after he turned 18 -- the age at which people can buy guns legally in Texas. Law enforcement officials are still investigating his motive.

In response to the shooting, President Joe Biden has stressed the importance of strengthening gun control in the United States.

But Abbott, a Republican, suggested at the news conference that gun control was not an issue in the incident.