President Donald Trump said Thursday he's planning to meet with families and officials in Parkland, Florida, where a gunman massacred 17 people at a high school.

Trump made the announcement during a nationwide address from the White House during which he described a "scene of terrible violence, hatred and evil."

Trump has resisted calls for greater gun control measures after previous mass shootings, including the October rampage that killed 58 people in Las Vegas.

Seventeen people were slain and 14 people were hospitalized in Wednesday's rampage at Marjory Stoneman Douglas High School in Broward County, authorities said. The suspect, troubled 19-year-old former student Nikolas Cruz, was booked on 17 counts of premeditated murder Thursday. Authorities said he used an AR-15 assault rifle.

"We are committed to working with state and local leaders to help secure our schools and tackle the difficult issue of mental health," Trump said in his speech in which he made no specific reference to guns.

Trump will make the trip this weekend, when he was planning to be at his private Mar-a-Lago resort in Palm Beach 40 miles away. The White House said the timing of the visit to Parkland in Broward County was being worked out.

"Our Nation grieves," he said in a proclamation ordering flags to be flown at half-staff. No one "should ever feel unsafe in an American school," he said earlier in a tweet.

It was already the 18th — and deadliest — school shooting in 2018, more than twice as many as this time last year, according to a count by Everytown for Gun Safety, a gun control advocacy organization.

Trump tweeted his prayers on Wednesday night.

My prayers and condolences to the families of the victims of the terrible Florida shooting. No child, teacher or anyone else should ever feel unsafe in an American school.

He also said he had spoken with Florida Gov. Rick Scott.

Just spoke to Governor Rick Scott. We are working closely with law enforcement on the terrible Florida school shooting.

On Thursday, he said people should report suspicious behavior.

So many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior. Neighbors and classmates knew he was a big problem. Must always report such instances to authorities, again and again!

He later ordered flags to be flown at half-staff until sunset Monday, saying in a statement: "Our Nation grieves with those who have lost loved ones in the shooting at the Marjory Stoneman Douglas High School in Parkland, Florida."