Los Angeles: Two years after a gunman invaded an elementary school in Newtown, Connecticut, and opened fire with a Bushmaster AR-15 rifle killing 26 children and educators, the families of nine people who died in the attack have filed suit against the maker and sellers of the weapon, arguing it should not have been available for civilian use because it was too powerful.

In addition to Bushmaster, the defendants are Camfour, a firearm distributor, and Riverview Gun Sales, the store in East Windsor, Connecticut, where the gunman’s mother purchased the weapon in 2010. A spokesman for Bushmaster declined to comment, and calls to Camfour and Riverview Sales were not immediately returned.

The suit, announced on Monday, was filed in state court and alleges that the manufacturer and others were negligent in allowing the sale of the weapon, the civilian version of the M-16 used by the military. Adam Lanza used the weapon to kill 20 students and six educators at Sandy Hook Elementary School, then took his own life with a Glock handgun. He began his deadly spree by killing his mother, Nancy, in their home with a .22-calibre rifle.

“In order to continue profiting from the sale of AR-15s, defendants chose to disregard the unreasonable risks the rifle posed outside of specialised, highly regulated institutions like the armed forces and law enforcement,” the plaintiffs wrote in the complaint.

Connecticut law generally allows a two-year window in which families can file negligence or wrongful death lawsuits. According to the law firm of Koskoff, Koskoff and Bieder, which represents the plaintiffs, the complaint was delivered to a Connecticut state marshal Saturday.

The plaintiffs include the families of 29-year-old Rachel D’Avino, a behavioural therapist who had recently started working at Sandy Hook; Victoria Soto, 27, a first-grade teacher; Daniel Barden, 7, who aspired to be a firefighter and whose casket was saluted by firefighters during his funeral; and Benjamin Wheeler, 6, who couldn’t decide whether to be an architect, paleontologist or a lighthouse keeper. Natalie Hammond, a teacher who survived after being shot in the foot, leg and hand, is also one of the plaintiffs.

Despite the military-grade firepower of the weapon, Bushmaster, Camfour, and gun shops have promoted its use by civilians and made large-capacity magazines compatible and accessible to the general public, the lawsuit alleges, contending that doing so caused an “unreasonable and egregious risk of physical injury to others.”

The attack turned Newtown into a symbol for those seeking tighter gun control. But a recent poll from the Pew Research Centre shows that public support for gun rights has surpassed support for more gun control.

Fifty-two per cent of those surveyed said it’s more important to protect the rights of Americans to own guns, while 46 per cent say it’s more important to control gun ownership. It’s the first time in more than two decades that the Pew survey has found more support for gun rights than gun control.

A Pew survey in January 2013, a month after Sandy Hook, found that 51 per cent of Americans said gun control was needed, compared to 45 per cent who said it was more important to protect the rights of people who own guns.