Nearly two weeks after the attack in Parkland, Florida left 17 people dead, US lawmakers reconvened after a one-week recess under intensifying pressure to address gun violence.
Trump has since called for reforms including tougher background checks on firearm purchases, but the White House has yet to announce support for specific legislation in Congress, where enacting federal gun restrictions faces major obstacles especially in an election year.
During a White House meeting with state governors, Trump said he would have felt compelled to confront the shooter.
"I really believe I would run in there even if I didn't have a weapon," Trump said. "You never know until you're tested."
Having previously criticized an armed deputy who failed to intervene in the February 14 shooting at Marjory Stoneman Douglas High School, Trump also branded the performance of some local law enforcement "frankly disgusting."
The deputy, Scot Peterson, pushed back through his lawyer, saying he positioned himself outside a school building because he believed the shots were originating from outside.
"The allegations that Mr Peterson was a coward and that his performance, under the circumstances, failed to meet the standards of police officers are patently untrue," lawyer Joseph DiRuzzo said in a statement. Spurred to action by the shooting -- the worst at a US school in six years - several Parkland survivors travelled to the US Capitol, where they met Monday with top House Democrat Nancy Pelosi and other lawmakers.
Trump, who touted his Second Amendment credentials on the 2016 campaign trail, said he lunched Sunday with Wayne LaPierre, the head of the powerful National Rifle Association, and told him changes were needed.
"We're going to do strong background checks. Very strong," Trump told the governors. "If we see a sicko, I don't want him having a gun."
Trump has also called for boosting school security, and controversially, arming some teachers and staff in addition to on-campus guards.
Most Democrats want gun control efforts brought to fruition in Congress, and a new CNN poll showed that 70 percent of Americans support stricter gun laws, up 18 points since October.
But it remains unclear just what measures can pass Congress in Washington's overheated partisan fog, and Republican House and Senate leaders have remained largely silent on the issue.
Senate Republican Pat Toomey and centrist Democrat Joe Manchin want to reprise their 2013 bill that would expand background checks to include purchases online and at gun shows.
Manchin told reporters Trump would need to express his support for the measure for it to pass the Republican-controlled Senate.
Republicans from suburban districts, where calls for gun control have gained ground, have expressed openness to raising the age limit for purchasing semi-automatic rifles from 18 to 21, or banning devices that turn such weapons into machine guns.
Senator Susan Collins, a Republican moderate, said she also supports expanding background checks and addressing mental health.
"I definitely want to see the issue taken up," she told AFP.
But many conservatives consider any tightening of gun laws a creeping assault on citizens' constitutional right to bear arms.
"I don`t think we need more gun control, I think we need better idiot control," said Senator John Kennedy of Louisiana.
The split appeared to leave the prospects of significant new gun legislation in doubt.
Some Republicans are pushing the so-called "Fix NICS" bill which would compel agencies to report information into the National Instant Criminal Background Check System.
"We must do much more than that," said top Senate Democrat Chuck Schumer as he touted legislation that expands background checks.
Doing so, he said, would require Republicans to "break free from the iron grip of the NRA."With the gun debate raging, Parkland students and teachers made an emotional return to their school Sunday, setting foot on site for the first time since the massacre.
Staff returned to work on Monday, and classes were to resume Wednesday.
Parkland`s students, in the spotlight as they spur the conversation on guns, received praise Monday from First Lady Melania Trump, who said she was "heartened to see children across this country using their voices to speak out and try to create change."
"They are our future and they deserve a voice," she said.