Neil Heslin, whose six-year-old son was murdered at Sandy Hook Elementary School last month, was heckled by gun advocates during a legislative hearing on Monday.

"Changes have to be made," he told Connecticut lawmakers in an emotional testimony. "I'll tell you a little bit about Jesse. He was a boy that loved life, lived it to the fullest. His mother and I are separated. He spent equal time with both of us. He was my son, he my buddy, he was my best friend, and I never thought I would be here speaking like this, asking for changes on my son's behalf."

"And I never thought I would be laying him to rest. The happiest day of my life was the day he was born. He is my only son, my only family. The worst day of my life was the day when this happened."

He said firearms like the popular AR-15/M16 rifle were designed to "put a lot of lead out on the battlefield quickly." When Heslin asked why anyone should be allowed to own a semi-automatic rifle like the one used to kill 26 people in Newtown last month, angry gun advocates shouted, "the Second Amendment!"

"We're all entitled to our own opinions and I respect their opinions and their thoughts," Heslin said. "But I wish they'd respect mine and give it a little bit of thought."

Helsin said he grew up with guns and doesn't believe they should be completely prohibited. But he supports the proposed assault weapons ban and restrictions on high-capacity magazines to prevent mass shootings like the one that killed his son.

“That wasn’t just a killing. That was a massacre,” he said. “Those children and those victims were shot apart. And my son was one of them.”

Thousands of people gathered at the Capitol to attend the public hearing of the Bipartisan Task Force on Gun Violence Prevention and Children's Safety, the second of four the state legislature is holding. While Heslin and other parents affected by the tragic Newtown shooting called for additional gun control measures, other parents said mass shootings couldn't be prevented by more laws.

"I believe in a few simple gun laws. I think we have more than enough on the books. We should hold people individually accountable for their actions,” said Mark Mattioli, whose six-year-old son was killed at Sandy Hook.

Watch video, uploaded to YouTube, below:

Watch a short clip, uploaded to YouTube by the Associated Press, below:

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[Ed. note: Updated after publication to include Heslin's full testimony]