US President Donald Trump on Friday visited a Florida hospital to offer comfort to those wounded in a mass school shooting, after the FBI admitted it mishandled a tip about the troubled teen behind the massacre that left 17 dead.
The arrival of Trump and his wife Melania came at the end of a difficult day for the families of those killed in Wednesday's rampage at a high school in Parkland, Florida, who learned that the carnage could perhaps have been averted.
The FBI admitted it had received a chilling warning in January from a tipster who said the 19-year-old gunman, Nikolas Cruz, could be planning a mass shooting, but that agents had failed to follow up.
At Broward Health North Hospital, where Trump met with survivors of the shooting, the president thanked the doctors, nurses and first responders for their "incredible" work, and described the carnage as "very sad."
He and his wife then headed to the Broward County sheriff's office, where they met with Florida Governor Rick Scott, Senator Marco Rubio, Sheriff Scott Israel and other law enforcement officers.
Trump told the group he had met with a female survivor who had been shot four times, including in the lung, adding that quick first responders had saved her life.
"Give them a raise," he said.
He later tweeted several pictures of himself and Melania, visiting with a survivor and her family, as well as posing with hospital staff.
The president's visit to the Parkland area north of Miami came amid growing anger among parents and students at Marjory Stoneman Douglas High School over America's seeming unwillingness to toughen gun control laws.
The FBI made a stunning admission earlier in the day, saying a "person close to Nikolas Cruz" made a call to the agency's public tipline on January 5 to "report concerns about him."
"The caller provided information about Cruz's gun ownership, desire to kill people, erratic behaviour, and disturbing social media posts, as well as the potential of him conducting a school shooting," the FBI said in a statement.
The information from the caller "should have been assessed as a potential threat to life" and forwarded to the agency's Miami field office, it said.
Instead, "no further investigation was conducted."
Trump's visit to the Parkland area - not far from his Mar-a-Lago resort, where he will spend the long President's Day weekend - was not announced in advance, perhaps because he risked being greeted with angry demands for action on gun laws.
"It's illogical that the law says a minor can't have a drink, but can buy a gun," said 47-year-old Mavy Rubiano, whose child survived the shooting.
In Washington, the political response so far makes it clear that the powerful pro-gun National Rifle Association, which spent $30 million to support Trump's election in 2016, remains formidable.
As with previous mass shootings, the focus of gun control advocates was the easy availability of the AR-15, a civilian version of the US military's M16.
Millions have been sold around the United States, and AR-15-style rifles were used in the mass shootings in Las Vegas, Sutherland Springs, Texas and Newtown, Connecticut.