Fred Guttenberg, whose daughter Jamie was murdered during the Marjory Stoneman Douglas High School shooting last week in Parkland, Florida, challenged Republican Sen. Marco Rubio on Wednesday for his positions on gun control.

"Sen. Rubio. My daughter, running down the hallway at Marjory Stoneman Douglas, was shot in the back with an assault weapon -- the weapon of choice. OK?" he asked, speaking at the CNN town hall "Stand Up: The Students of Stoneman Douglas Demand Action" in Sunrise, Florida.

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

Rubio replied that he believed Guttenberg was telling the truth and that someone like the confessed killer should not have had access to any firearm, but that the assault weapons ban was too easily circumventable and poorly crafted.

"I believe that someone like this individual and anyone like him shouldn't have any gun," Rubio said. "I absolutely believe that in this country if you are 18 years of age, you should not be able to buy a rifle, and I will support a law that takes that right away."