WASHINGTON (NYTIMES) - The father of a 14-year-old girl gunned down at a Florida high school angrily lectured Senator Marco Rubio - in a nationally televised forum attended by thousands of students, teachers and others - for his refusal to back gun control legislation.

The father, Fred Guttenberg, demanded that Rubio - a Republican Party member and previously Speaker of the Florida House of Representatives - explain his opposition to a ban on the kind of assault weapon that a gunman at Marjory Stoneman Douglas High School used to shoot his daughter, Jaime, in the back.

"My daughter, running down the hallway, was shot in the back with an assault weapon, the weapon of choice," Guttenberg said during the CNN town hall-style meeting as Rubio stood stone-faced.

"It is too easy to get. It is a weapon of war. The fact that you can't stand with everybody else in this room and say that, I'm sorry."

The room erupted in applause for Guttenberg and repeatedly booed as Rubio sought to explain his opposition to a proposed assault weapons ban. The Bill, he said, is riddled with loopholes that would make it easy for criminals to get around.

"First, you have to define what it is. It basically bans 220 specific models of gun," Rubio said, prompting applause from the audience.

He continued, saying that the Bill also allows for "2,000 other types" of guns that operate the same way, but are not classified as assault weapons.

Rubio had offered opening remarks that he clearly hoped would deflect criticism during the event. He expressed grief for those who were affected by the shooting at Stoneman Douglas, in Parkland, Florida, but he said that people in the United States needed to find ways to disagree "without accusing one another of being evil people".

But the audience, and Guttenberg, did not hold back in criticising Rubio's position on gun control.

Guttenberg repeatedly asked whether Rubio believed that "guns were the factor in the hunting of our kids".

The senator said he agreed, but he insisted that other types of laws would better prevent such attacks in the future. He said that he would support a Bill to increase the minimum age for the purchase of an assault weapon to 21 from 18.

And he said that he backed improvements to background checks and a ban on bump stocks, which can convert semi-automatic weapons to fire automatically.

Students and teachers at the event also had questions for Florida's other politicians, including two Democrats, Senator Bill Nelson and Representative Ted Deutch.

One young student talked about how her best friend was gunned down in front of her, and she asked Nelson about background checks, and how to improve them.

Another student, whose brother was killed in the shooting, bluntly said to Deutch that "my friends and I are worried that we are going to be murdered in our classrooms". He asked what Deutch was going to do about it.

"As a starter," the congressman said, "I'm going to introduce legislation to make sure that assault weapons are illegal in every part of this country." The audience burst out in applause.

But Rubio, who ran for president in 2016, was the primary target of ire from people at the forum, who repeatedly challenged the senator's positions on gun control and his willingness to accept donations from the National Rifle Association.

The issue of donations was raised by a junior at the high school, who stood just feet from Rubio and asked him whether he would renounce money from the gun advocacy group in the future.

When Rubio refused, the audience booed loudly.

"People buy into my agenda and I do support the Second Amendment," Rubio said, repeatedly refusing to say he would stop accepting money from the group. "The influence of these groups comes not from money, the influence comes from the millions of people who support the agenda."

Deutch at one point engaged in a brief debate with Rubio, saying that a gun that allowed the shooter to fire off 150 rounds in six to seven minutes "should be banned".

Later, Chris Grady, a student at the high school, thanked Rubio for appearing at the forum, unlike President Donald Trump and Rick Scott, the Republican governor of Florida, who both turned down invitations from CNN to participate.

"A lot more than can be said for our so-called president and governor," Grady told Rubio. "We need you and your colleagues on both sides to come together with us and find a compromise if we are ever to solve this epidemic that is plaguing our country."

Grady asked the senator whether he supported legislation to limit high-capacity magazines that allow weapons to fire many bullets quickly. Rubio said that he had long opposed such legislation, but was now reconsidering that position.

Rubio said there would be evidence from the Florida school shooting that suggested the shooter might have killed fewer people if he did not have high capacity magazines.

"It wouldn't have prevented the attack, but it would have made it less lethal," the senator said.