PORTLAND, Ore. — Three years ago a 30-year-old mentally ill man fatally shot a Castro Valley woman as she admired a scenic view on the Oregon coast, using one of three weapons acquired by the killer’s mother from gun dealers.

The family of the dead woman, 57-year-old Kirsten Englund, filed a wrongful death lawsuit earlier this year against two gun dealers who sold the firearms and against the killer’s mother, Diane Boyce.

And now the mother of murderer Jeffrey Boyce has agreed to pay $400,000 to Englund’s family and has also provided documents to assist in their lawsuit against the two gun dealers, the family’s attorneys said Thursday.

The lawsuit states that Diane Boyce had acted as a “straw purchaser” to acquire weapons for her son, which is against the law, and contends that the two gun dealers failed to heed “red flags” that Jeffrey Boyce was the actual purchaser.

Jeffrey Boyce committed suicide by hanging himself in a California jail cell about three months after his arrest.

Lawyers for the Englund family on Thursday filed an amended complaint that includes information provided by Diane Boyce.

Named in the lawsuit are the World Pawn Exchange in North Bend, Oregon, and J & G Sales, Ltd. Of Arizona, which sells firearms online.

The complaint states that Jeffrey Boyce of Coos Bay, Oregon, ordered the three firearms over the Internet and had them delivered to World Pawn Exchange in nearby North Bend.

It states that Jeffrey Boyce would not have been able to legally purchase those guns himself because he had a felony conviction for unlawful use of a weapon and because of his mental health issues.

It says that Jeffrey Boyce created a customer account with J & G for purchasing two of the weapons, including the handgun used to kill Kirsten Englund, and there is more purchase documentation that makes it explicitly clear he was the actual buyer.

Diane Boyce picked up the three weapons from World Pawn Exchange over a three-month period — from Dec. 12, 2011 to Feb. 27, 2012.

“In the face of clear evidence that Diane Boyce was acting as a straw purchaser for her son, Jeffrey Boyce, neither WPE nor J&G performed a review of their own firearms records, “the complaint states.

World Pawn Exchange said owner Richard Sinatra would not comment on the pending litigation. J & G Sales said the person there who would comment was not available until next week.

Diane Boyce’s attorney, Marty Rall, did not immediately return a call.

Kirsten Englund, a retired auditor, was killed in April 2013 while on a road trip to visit relatives in the Northwest. Her body was found near her car at a Pacific Ocean overlook. Boyce was arrested in Northern California after carjacking a man at gunpoint.

Diane Boyce had called police to warn that her son was mentally ill. Jeffrey Boyce told her in a phone call that he was driving south to seek political asylum at the Russian Consulate in San Francisco.

Kirsten Englund’s two sons, Andrew and Nicholas Wiegardt, said they still feel the pain from the loss of their mother.

“It’s hard to bring back all these memories,” Andrew Wiegardt said in a phone interview.

Their attorney in the lawsuit, Linda Singer, said: “Had these gun sellers followed the law, these sales would not have happened and Kirsten Englund would not have suffered a brutal death.”