The father of a teenager who used his dad's gun to kill four classmates and then himself at a Washington state high school was sentenced Monday to two years in prison on firearms charges.

Raymond Fryberg apologized for his son's actions in U.S. District Court. He was convicted in September of illegally owning six firearms, including the gun that his 15-year-old son, Jaylen, used in the 2014 school shooting.

A domestic violence protection order filed by Raymond Fryberg's former partner in Tulalip Tribal Court should have kept him from owning a gun. But a record of the 2002 order never made it into any state or federal criminal databases used by firearms dealers conducting background checks during gun purchases.

The case revealed flaws in the way federal authorities and tribal governments share information and led to 10 American Indian tribes gaining access to national criminal databases. The tribes, including the Tulalip tribes in Washington, can now conduct thorough background checks and add criminal records to the databases.

Prosecutors say Fryberg lied on a form he filled out when he bought the guns to hide the restraining order. His lawyers said he didn't know he was prohibited from having firearms, and they sought probation as punishment.

The sentence was closer to prosecutors' request for 33 months in prison.

Fryberg acquired nine firearms between November 2012 and July 2014, prosecutors say.

He bought a Beretta pistol on Jan. 11, 2013, from a gun shop on the reservation, according to a criminal complaint. He answered "no" on the federal firearms purchasing form when asked if he was the subject of a restraining order that prohibits him from "harassing, stalking or threatening your child or an intimate partner," the complaint said.

Fryberg's lawyer, John Henry Browne, said "there was never an order prohibiting him from owning or even purchasing firearms" from the tribal court. The issue in court will be whether he lied on the federal purchasing form, Browne said.

Fryberg's son used one of those guns at Marysville Pilchuck High School north of Seattle to kill four classmates and seriously injure another before turning the gun on himself on Oct. 24, 2014.

Five families of the teens shot at the school filed a $110 million lawsuit Friday against Fryberg and the school district.