Mr Trump last week launched a stinging attack on sheriff’s deputy Scot Peterson, branding him a “coward” for failing to enter the school to confront the gunman, who killed 17 teenagers before being arrested at the scene.
He added that Mr Peterson has “choked” and “didn’t have the courage”.
And he returned to the subject during a meeting of US governors at the White House, insisting he would have entered the building “even if I didn’t have a weapon”.
He added: ”You don’t know until you test it, but I think, I really believe I’d run in there, even if I didn’t have a weapon, and I think most of the people in this room would have done that too.”
Mr Trump suggested that more than one sheriff’s deputy was at fault, adding that the officers who remained outside “weren’t exactly Medal of Honor winners”.
He sneered: “The way they performed was frankly disgusting.”
Mr Trump’s remarks came as he addressed a gathering of US governors at the White House, during which he stressed a need for action in the wake of the Parkland school shooting and listened to governors’ proposals.
He has indicated support for raising the minimum age to purchase semiautomatic rifles, improving the background check system and providing teachers with guns.
However, he has not yet outlined any specific legislation to achieve these objectives.
Last week he lashed out at the FBI on Twitter, saying they had “missed all of the many signals” that the shooter had been poised to go on a murder spree.
He also attempting to link the incident to the probe into potential collusion between his election campaign and Russia.
It was reported last week that, apart from Mr Peterson, three other sheriff’s deputies had their pistols drawn and were behind their vehicles but did not enter the school.
In a statement issued today, Mr Peterson’s attorney rejected the criticisms, saying “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.”
The tragedy, at Marjory Stoneman Douglas High School, has reopened the debate about gun control in the United States.
Teenagers travelled to the Florida state capital of Tallahassee to join protest about the situation and called for action on Twitter via the #NeverAgain hashtag.
Meanwhile in a press conference on Friday, Wayne LaPierre, chairman of the influential National Rifle Association, took the opportunity to accuse the Democratic Party of pushing a “socialist” agenda to deprive gun owners of their weapons.