Ellen’s, the Dallas restaurant that was the target of a boycott by the National Rifle Association earlier this month, donated $15,000 over the weekend to a grass-roots group founded in the wake of the 2012 Sandy Hook Elementary School massacre.

A check was presented to representatives of Moms Demand Action for Gun Sense in America at a Mother’s Day ceremony at Ellen’s on Sunday.

The money was collected from sales and donations from customers who were angry when the N.R.A. urged members to boycott Ellen’s, after it expressed support for “reasonable” gun regulations ahead of the association’s annual convention in Dallas from May 4 to 6.

“Ellen’s has always maintained their full support of Second Amendment rights, along with an understanding that we must protect our children in schools and police officers in the line of duty,” the restaurant posted in its Mother’s Day message.

The N.R.A. did not return an email seeking comment on Monday.

The restaurant explained that many of the restaurant’s staffers were affected after a gunman targeted and killed five police officers in July 2016 at a peaceful protest in Dallas.

“Ellen’s wanted not only to honor those fallen officers, but also to find ways to support efforts to prevent such tragedies from happening in the future,” the post said.

In the week ahead of the N.R.A. convention, Ellen’s included a message at the bottom of its customers’ sales receipts explaining that some of the proceeds earned then would be donated to organizations “dedicated to implementing reasonable and effective gun regulations.”

“Perhaps I am naïve, but I didn’t think words like ‘reasonable’ and ‘effective’ were firebrand words,” said Joe Groves, a managing partner of Ellen’s, in an interview on Monday.

Ellen’s quickly became the target of verbal and online threats, fake reviews and harassing phone calls after the N.R.A. urged its members to boycott. Mr. Groves said one caller, who identified himself as an N.R.A. member, warned of a plan to “shoot up” the restaurant and, in particular, kill Mr. Groves.

Mr. Groves recalled, “I said, ‘If I’m going to be murdered, is it going to be by a criminal or a law-abiding citizen?’” The caller grumbled and hung up.

Mr. Groves said he grew up in a family that hunted and included members of the N.R.A. In recent years, though, he said the organization has become more focused on lobbying, gun sales and politicizing gun ownership in an attempt to frighten owners into thinking that other Americans want to take their guns away.

“That is simply not true,” he said. “This experience has hardened my position.”

Mr. Groves said he asked the public about what organizations should get the restaurant’s $15,000 check. Several people suggested Moms Demand Action, which was founded in 2012 by Shannon Watts, a former communications executive, in response to the shooting at Sandy Hook in Newtown, Conn., which left 20 schoolchildren and six adults dead. The grass-roots network has quickly grown into a leading force for gun violence prevention, with chapters in 50 states.

“Most Texans, including gun owners, agree that we’re all safer with some common sense gun laws in place,” said Donna Schmidt, a volunteer with the group’s Texas chapter. “The N.R.A.’s radical leaders oppose common sense, and we’re grateful to Ellen’s for standing with the rest of us. The ground is shifting, even here in Texas.”