(CNN) - When Sen. Kelly Ayotte was defending her vote on Tuesday on a recent gun control proposal, she was confronted by the daughter of a victim in the Newtown, Connecticut, elementary school massacre.
Speaking at her first town hall event in New Hampshire since the gun vote earlier this month, the Republican senator sought to explain why she voted against a measure that would expand background checks on firearms sales.
But the crowd of gun control advocates and opponents created a tense environment.
At one point, Erica Lafferty, daughter of slain Sandy Hook principal Dawn Hochsprung, asked Ayotte why she voted against the background check amendment, which was created from a bipartisan compromise but failed to gain the 60 votes needed to move forward in the Senate.
Lafferty told Ayotte that on the day the senator voted, she said the legislation would be a burden on gun store owners, according to CNN affiliate WMUR. "I'm just wondering why the burden of my mother being gunned down in the halls of her elementary school isn't as important."
A lone gunman opened fire at Sandy Hook last December, killing 20 children and six educators.
Lafferty was among the Newtown families who traveled to Washington this month to lobby senators to pass tougher gun laws. Only four Republicans voted against their party and in favor of the bipartisan compromise background check measure. One of them, Sen. Susan Collins of Maine, was among those who met with Newtown families before the vote.
On the day of the Senate vote, Lafferty told CNN she was disappointed but felt confident that the bill will rebound. Until then, she added, lawmakers will be held accountable.
“The next time there's a mass shooting and they're asked what they did to prevent it, they're going to have to say nothing,” she said.
Taking a soft tone on Tuesday, Ayotte expressed condolences for the loss of Lafferty's mother.
"I think that ultimately when we look at what happened in Sandy Hook we should have a fuller discussion to make sure that doesn't happen again," the senator said. Ayotte argued the current system needed better enforcement.
"Mental health is the one area that I hope we can agree on going forward to work on because that seems to be the overriding issue on the list and that is why I have been trying to work across the aisle on that issue."
- CNN’s Lisa Desjardins contributed to this report.