Early Friday morning, the couple, Scott and Buckley Kuhn-Fricker, were shot in their home by the teenager, police said, who then shot himself.
Fairfax County Police spokeswoman Reem Awad said the suspect, whose name is being withheld by police because he is a minor, is hospitalized in critical condition with life-threatening injuries. He is under police guard.
Four other family members who were in the home at the time were uninjured.
Buckley Kuhn-Fricker recently discovered private tweets on her daughter's phone that concerned her. The tweets, which she believed were connected to the boyfriend, included one that responded to a photo of a candy shop featuring a Jewish dreidel with the comment "ima run in there with my swastika armband right now," the Washington Post reported
The mother, according to the Post, wrote to the principal of the school that her daughter and boyfriend attended, warning him of her concerns. She sent the principal images showing a Twitter account that had retweeted messages praising Adolf Hitler, supporting Nazi book burnings and making derogatory comments about Jews, the Post reported.
The mother, the paper reported, believed the messages were posted under an assumed name but that the account belonged to her daughter's boyfriend. The Post said it could not independently confirm the account was tied to the boyfriend. CNN was not able to verify the information about the account.
Buckley Kuhn-Fricker's mother, Janet Kuhn, told the paper her daughter believed the boyfriend was trying to indoctrinate the girlfriend with white supremacist ideas. Kuhn told the paper the family staged an intervention with her granddaughter last week and thought the relationship was over. But early Friday morning, the couple discovered the boyfriend was in the house and he shot them, according to what Kuhn said she was told by police, the Post reported.
When reached by CNN, Kuhn said she preferred not to talk about the incident right now.
Police have not made public the motive for the shootings or the relationship between the suspect and the victims.
Friends tell CNN the family believes the incident sends a message about Nazi evil.
Buckley Kuhn-Fricker was a non-practicing lawyer who owned a company that provided care to older adults. Her husband, Scott, was a statistician with the US Bureau of Labor Statistics.