On Thursday Trump said he was making plans to meet with families in Parkland, Florida.

In televised remarks from the White House, Trump, who has an 11-year-old son, said he wanted to address America's children with the message they are "never alone and you never will be".

"You have people who care about you, who love you, and who will do anything at all to protect you," he said.

Democrats have said the shooting underscores the need for tougher gun laws, but Trump did not mention the issue in his brief address, delivered from the White House.

He said he would make school safety the top priority when he meets with governors and state attorneys general later this month.

"We must also work together to create a culture in our country that embraces the dignity of life, that creates deep and meaningful human connections," Trump said, urging children who feel scared or alone to reach out to trusted adults for help.

"We are here for you, whatever you need, whatever we can do to ease your pain," he said.

Trump did not speak out immediately after the shooting. He weighed in on Twitter early on Thursday, calling the suspect "mentally disturbed" and stressing it was important to "report such instances to authorities, again and again!"

The president has dealt before with the all-too-familiar ritual of offering consolation after horrific violence.

In the wake of a Las Vegas shooting in October that killed at least 58 people, Trump spoke from the White House Diplomatic Room, calling it an "act of pure evil', and seeking to help the nation heal.

In the past, he has largely focused on mental health as a cause for mass shootings, dismissing questions about gun control.

After a shooting at a Texas church left 26 people dead in November, the president also said "mental health" was the problem, adding that "this isn't a guns situation".

Australian Associated Press