By Maegan Vazquez, Kevin Liptak and Jeremy Diamond, CNN

(CNN) -- President Donald Trump on Thursday spoke directly to schoolchildren, teachers and families across the country in the wake of the Florida school shooting, saying the nation is "in grief."

"My fellow Americans, today I speak to a nation in grief," Trump said. "Our entire nation with one heavy heart is praying for the victims and their families. To every parent, teacher and child who is hurting so badly, we are here for you, whatever you need, whatever we can do, to ease your pain. We are all joined together as one American family and your suffering is our burden also."

"No child, no teacher should ever be in danger in an American school. No parent should ever have to fear for their sons and daughters when they kiss them goodbye in the morning," Trump added.

Earlier Thursday, Trump highlighted the apparent mental instability of the gunman who allegedly killed 17 people at a Florida high school.

"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!" Trump tweeted.

He also offered condolences on Twitter Wednesday in the aftermath of the massacre and issued a statement ordering flags to be lowered to half-staff on Thursday morning.

There were some discussions at the White House on Wednesday night of a presidential statement on the shooting, but ultimately Trump and his team decided it was too early in the proceedings for him to appear on-camera, according to an official.

The White House is still collectively working through how to best strike a "comforter in chief" tone after a year in office, this official conceded. Some advisers encouraged Trump to speak Wednesday night to demonstrate leadership but ultimately the decision was made that Trump was better off waiting until more facts were known about the massacre.

Trump has had some missteps in this area since becoming President, which the official attributed to his personality.

"He can be a warm guy but doesn't always say the right thing," the official said.

Trump's tweet Thursday morning wasn't run through top aides or advisers before he posted it, as is often the case.

Trump's aides are in the initial planning stages of a visit to the Parkland community over the weekend when he's staying at Mar-a-Lago, less than 50 miles away from the shooting scene, the official said. A second official said the White House wants to determine if a presidential visit would hamper law enforcement efforts before making a final decision.

The mayor of Parkland, Christine Hunschofsky, reacted to Trump's tweet on Thursday when it was read to her by CNN's Alisyn Camerota on "New Day."

"If a solution was simple for these things, we would have found one already," she said.

Hunschofsky added that she hopes a shooting like the one in her town "never happens anywhere again" and going forward vowed to be more vigilant in talking to her community about posts on social media or disturbing behavior.

The only gun measure Trump has signed since taking office revoked an Obama-era rule that required the Social Security Administration to disclose information quarterly to the national gun background check system about certain people with mental illness. It's not clear whether that measure would have prevented Wednesday's massacre.

Warning signs

The suspect, Nikolas Cruz, a 19-year-old former student,is in custody. Cruz was previously expelled from the school for unspecified disciplinary reasons, officials said.

Cruz had a variety of gun and violence-related postings on social media sites, and Broward County Sheriff Scott Israel said his digital profile contained what he called "very, very disturbing" content.

Postings under the name Nikolas Cruz included threatening comments under videos on YouTube and other sites, including "I whana shoot people with my AR-15" (sic), "I wanna die Fighting killing s**t ton of people" and "I am going to kill law enforcement one day they go after the good people."

On his Instagram page, Cruz posted a photo of a shotgun, and in another photo, he is shown brandishing a pistol that appears to be a type of BB gun. In other pictures he is covering his face with a kerchief and brandishing long knives.

Police say Cruz was armed with multiple magazines and at least one AR-15 style rifle.

The suspected shooter bought the firearm in the past year and had passed the background check to make the purchase, according to a US official briefed on the investigation.

This story has been updated.

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