Golden State Warriors basketball coach Steve Kerr has used his pre-NBA playoff tip-off media conference to demand gun control change in the wake of the latest school shooting in Texas.

Kerr has spoken between the shooting this morning and before his side can close out the Western Conference finals series against the Mavericks in Dallas today.

Kerr's father was assassinated by terrorists in 1984 while he was the president of the American University in Beirut.

"Any basketball questions don't matter," a visibly upset Kerr said.

"Since we left shootaround, 14 children were killed, 400 miles from here, and a teacher. And in the last 10 days we've had elderly black people killed in a supermarket in Buffalo. We've had Asian church-goers killed in Southern California. And now we have children murdered at school. When are we going to do something?"

Meanwhile, the superintendent of a Texas elementary school where an 18-year-old gunman shot and killed 18 children and three adults said his heart is broken.

Hal Harrell, superintendent of the Uvalde Consolidated Independent School District, said Tuesday UST that Robb Elementary School will be closed and all school activities will be cancelled until further notice. Harrell also said grief counselors would be available starting Wednesday morning.

Police walk near Robb Elementary School following a shooting in Texas. Photo / AP

"My heart is broken today," Harrell said. "We're a small community and we're going to need your prayers to get through this."

The death toll increased today. State Sen. Roland Gutierrez said he'd been briefed by state police on the latest fatalities from the school in Uvalde, a heavily Latino community about 85 miles west of San Antonio.

In addition to 21 dead, three people injured in the shooting remain in serious condition, Gutierrez told The Associated Press. The gunman is dead, likely killed by police.