A Fourth of July barbecue in New Jersey turned deadly two years ago when 23-year-old Xavier Cuevas-Soto was killed after shooting himself with an off-duty cop’s unsecured gun.

Now, the young man’s mother and sister are suing the Paterson Police Department for allegedly spinning his death, which they claim was a tragic accident, into a suicide tale. The federal lawsuit, which was filed Monday, alleges that officers within the department and Sergeant Christopher Benevento, who left his weapon unattended at the party with the safety lock off, made up the suicide story, engaging in a “civil conspiracy” to avoid blame for Cuevas-Soto’s death.

“This entire event was easily avoidable and should have been avoided by following the most simple and obvious security procedures for the handling of guns, not only by a police officer, but by anyone owning a gun,” the family’s attorney, Shelley Stangler, told The Daily Beast.

The family is suing for state created danger, wrongful death, emotional distress, and negligence, among other claims, according to a complaint.

The Paterson Police Department has not responded to The Daily Beast’s requests for comment, but Director Jerry Speziale, who is listed as a defendant in the lawsuit, told NorthJersey.com, “Anytime there’s a loss of life, it’s tragic and regrettable.” Speziale also told the outlet he cannot comment on pending litigation.

In July 2016, Benevento invited the Soto family and about 20 others to an Independence Day party in Totowa, New Jersey, according to the lawsuit. At one point during the party, Benevento “left his loaded, police-issued handgun, with the safety lock in the off position on a porch railing outside his home,” the lawsuit states.

When a 6-year-old child reached for the gun, the officer moved the gun to a ledge, but his weapon remained exposed and unlocked, according to the lawsuit.

The officer had “actual knowledge that the gun posed a danger to his guests, but thereafter, in a gross dereliction of duty and in gross violation of policy, failed to holster it, put it in a lock-box or other secured location and failed to activate the safety,” according to the complaint.

Meanwhile, Cuevas-Soto was in “good spirits during the party, helping to set up tables and talking and laughing with guests while waiting for the steak to be done cooking,” the complaint states.

As he was talking with friends, Cuevas-Soto picked up the weapon to examine it, at which point it “accidentally discharged, killing him,” in front of his mother, Yolanda Soto, and his sister, Adrianna Soto, the court papers state. The 23-year-old “died in terror,” his family says.

Soon after, police and emergency personnel arrived to the scene, where Cuevas-Soto was pronounced dead. Adrianna Soto claims that she saw Benevento remove the gun from the scene, thereby tampering with evidence, according to the lawsuit.

The medical examiner listed suicide as Cuevas-Soto’s official cause of death, the lawsuit states. Initial investigations by the Passaic County prosecutor and Totowa police chief also concluded that Cuevas-Soto’s death was the result of an “apparent suicide,” NorthJersey.com reported.  

Benevento, who was promoted to sergeant after the incident, was briefly suspended for carrying an unsecured weapon.

According to the complaint, Cuevas-Soto’s death “severely and permanently emotionally scarred” his family, so much so that his mother—who fainted at the barbecue when she saw her son’s lifeless body—has attended therapy ever since.

“The family remains crushed and relives this nightmare daily,” Stangler said. “The mother does not stop crying over the loss of her young son.”