OLDSMAR — A longtime gun dealer agreed to abandon the industry on Friday to settle a lawsuit brought by a national gun-control group that argued his store should be held liable for selling a firearm to a mentally ill man who used it to kill his mother and her boyfriend in 2012.

Owner Gerald Tanso, 61, has sold his Oldsmar gun store, Lock N Load, and promised to never engage in the business of selling firearms again, said Jonathan Lowy, an attorney with the Brady Center To Prevent Gun Violence.

The remainder of the settlement is confidential. But Lowy said Tanso also agreed to make a public statement urging gun dealers to adopt stringent background checks, security measures and other practices to prevent straw purchasers and criminals from obtaining firearms.

Tanso's statement says, in part: "Our Second Amendment protects the rights of law abiding citizens and we must protect those rights. At the same time, we must exercise great caution and due diligence with great responsibility in preventing firearms from getting in the wrong hands of people who seek to harm us all. I support laws that protect our Second Amendment and the laws that protect our society from criminal elements who would abuse that right to the detriment of others. I encourage all gun dealers, including the new owner of my gun shop, to implement such measures."

Attempts to reach Tanso on Friday were unsuccessful. He initially called the complaint "a bogus lawsuit" when it was filed.

The Brady Center, named for James Brady, the White House press secretary who was shot during the 1981 assassination attempt on President Ronald Reagan, filed the Pinellas County suit in October 2014. The suit was filed nearly two years to the day after 18-year-old Benjamin Bishop killed his mother, Imari Shibata, and her boyfriend, Kelley Allen, in their Oldsmar home.

Bishop's father, Joey Bishop, and Allen's mother, Jean Allen, are listed as plaintiffs on the Brady Center's lawsuit, which says Tanso should be held liable for the mentally ill teen obtaining the sawed-off, 12-gauge shotgun used in the killings.

Both declined to comment for this story through their attorney, Evan Goldenberg.

Bishop was angry that his mother told him to get a job and take his schizophrenia medication, so he fired eight rounds at the couple as they lay in bed then called 911, authorities said.

Bishop, a diagnosed schizophrenic, was sentenced in 2015 to two consecutive life sentences in prison.

Bishop couldn't legally buy the gun because he had a criminal record and had even been turned away from Lock N Load when he attempted to buy one while on probation earlier that fall, according to the lawsuit. But in October, Bishop returned to Lock N Load with his neighbor, Matthew Schwab, 18, the lawsuit states. Schwab bought the shotgun with $279 in cash and then turned it over to Bishop, who told him he needed it to defend himself from gang members. Schwab never faced charges.

"Nationally, Florida's gun laws would be on the lax side; there's certainly more the state could do to protect its people from the dangers of guns winding up in the wrong hands," Lowy said. "This settlement gets to the heart of what gun dealers can do today to make us all safer, and it's very significant that Mr. Tanso has now openly embraced these responsible business practices and is encouraging others in the gun industry to follow suit."

Shortly after the gun was purchased, the store sold Bishop ammunition despite having recently run a background check on the teen, the lawsuit states. Such a search would have revealed that in 2011 Bishop was prosecuted in juvenile court for bringing a knife to Tarpon Springs High School and that same year pleaded guilty to a misdemeanor domestic battery charge for choking his mother. Bishop also had a history of hospitalizations under the Baker Act and was addicted to synthetic drugs, the lawsuit says.

Bishop isn't the only one to purchase a murder weapon from Lock N Load.

Court records show that another accused killer, Tampa mother Julie Schenecker, passed a background check at Lock N Load before purchasing a firearm from the store that was later used in the murders of her two children in January 2011. Schenecker was convicted of first-degree murder and is serving two concurrent life sentences in prison.

Lock N Load hasn't shuttered its doors, said its new owner, Dominic Zingale.

Zingale, a federally licensed firearm dealer, purchased the store from Tanso on May 15, he said. The sale was a condition of the settlement.

"I am and will continue to follow all of the applicable ATF, Florida, and local guns laws and procedures set forth by them to the letter," Zingale said in a written statement to the Tampa Bay Times. "I have no operational ties to the former owner nor have I worked with him when he was in the firearms business."

Contact Anastasia Dawson at adawson@tampabay.com or (813) 226-3377. Follow @adawsonwrites.