The Major Hunting and Outdoors Store at the Center of a Big Gun Lawsuit

Dawn Nguyen was sentenced to 16 months in prison Monday after pleading guilty last month to falsifying firearms forms in June 2010 at a Gander Mountain store Rochester, New York. There she was accompanied by William Spengler, who wasn't allowed by purchase a gun because he had previously been convicted of killing his 92-year-old grandmother with a hammer.

Nguyen paid $1,425 for two firearms, a semi-automatic rifle and a shotgun that Spengler eventually would use.

A wall of semi-automatic rifles is seen at the National Rifle Association (NRA) Annual Meetings and Exhibits April 14, 2012 in St. Louis, Missouri. AFP PHOTO / Karen BLEIER KAREN BLEIER/AFP/Getty Images

On Christmas Eve 2012, Spengler, 61, shot and killed his sister before he torched the home they lived in. When West Webster, New York firefighters responded, Spengler began shooting, killing two firefighters, Tomasz Kaczowka and Michael Chiapperini, and wounding two others, Ted Scardino and Joseph Hofstetter.

A day after Nguyen, now 24, was sentenced, the firefighters and surviving family members are alleging in a lawsuit filed in New York state court that the Minnesota-based Gander Mountain, the nation's largest outdoors and sportsman store, should have known the buyer was a straw purchaser, the Minneapolis Star Tribune reported.

The litigation could be far reaching given the size of the retailer, which has drawn the backing of gun control advocates. The families are being represented by the Brady Center to Prevent Gun Violence, a pro-gun control group.

In a joint statement, the plaintiffs said they first believed this was “yet another random act of violence."

“But as time went by, new and very troubling facts emerged,” the plaintiffs statement continued. “These facts suggest that the loss we have endured could have been avoided. If only the store had acted responsibly.”

The statement went on to assert the families respect the Second Amendment, and asserted some families are gun owners.

“But, we also believe that companies who make it their business to sell guns must do so in a responsible and lawful manner," the statement continued. "And when sellers fall short in their responsibility, they should be held accountable.”

A spokesman for Gander Mountain told the Star-Tribune the company had been forthcoming in the investigation and is committed to safety.

“We will vigorously defend ourselves in this matter,” spokesman Jess Myers said.

The suit claims the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) warned gun dealers that indicators of a straw purchase include multiple firearms being bought at once or more than one person entering the store together and paying with cash, which plaintiffs claim the store's staff should have known.