A federal jury on Friday found that the death of a woman shot by her former father-in-law at a Delaware courthouse in 2013 was the result of cyberstalking by the gunman's widow and two children, convicting the three defendants on all counts in a nationally unprecedented verdict.

Jurors reached their decision after a month-long trial, finding former optometrist David Matusiewicz; his mother, Lenore; and his sister, Amy Gonzalez, guilty of stalking resulting in the death of David's ex-wife, Christine Belford.

"It is an unprecedented verdict. It is the first of its kind in the country. We certainly believe it was appropriate charges," said Delaware's U.S. Attorney Charles Oberly III. "I just hope there is some sense of justice for the family."

Justice Department officials have said they believe there had until this case been no precedent for a person being convicted on federal charges of cyberstalking resulting in death, which carries a possible life sentence.

The defendants did not show any visible emotion when the verdicts were read Friday morning, but Amy Gonzalez began weeping as the jury left the courtroom, holding her hands in a prayer-like fashion against her forehead. All three are to remain in custody pending sentencing, set for Oct. 15.

Belford and a friend, Laura "Beth" Mulford, were killed by David's father, Thomas Matusiewicz, who then exchanged gunfire with police before killing himself. Belford and the friend were killed as they arrived for a child support hearing..

The defendants had denied knowing that Thomas Matusiewicz planned to kill Belford.

All three defendants were charged with cyberstalking and with conspiracy to engage in interstate stalking and cyberstalking of Belford.

Lenore Matusiewicz also was charged with two counts of interstate stalking based on trips to Delaware in 2011 and 2013, while David Matusiewicz faced a single count of interstate stalking for his trip to Delaware for the February 2013 child support hearing that Belford planned to attend.

The hearing was part of a long and bitter court battle over the three daughters Belford had with David Matusiewicz, who went to federal prison and later lost his parental rights after he and his mother kidnapped the children and took them to Central America in 2007, purportedly because of concerns about abuse and neglect by Belford.

Prosecutors alleged that, after the kidnapping, David Matusiewicz conspired with his parents and sister over several years to spy on, torment and stalk his ex-wife, and that the family repeatedly and falsely accused Belford in emails, letters, phone calls and Internet postings of abusing and neglecting the couple's daughters.