The US Air Force must pay $230m in compensation over a 2017 mass shooting at a Texas church.
Former airman Devin Patrick Kelley killed 26 people, including the pastor's daughter, when he went on a shooting rampage inside the First Baptist Church of Sutherland Springs on 5 November 2017.
Another 20 were injured before Kelley turned the gun on himself.
Handing down his judgment on Monday, US District Court Judge Xavier Rodriguez said the case was "unprecedented in kind and scope", and that the pain and loss experienced by the families was "immeasurable".
"Ultimately, there is no satisfying way to determine the worth of these families' pain," he said.
Last year, Rodriguez held the US Air Force partially responsible for the attack after failing to report domestic violence charges against Kelley on a federal database - an oversight the courts said may have prevented him from legally buying the weapon used in the shooting.
"Had the government done its job and properly reported Kelley's information into the background check system — it is more likely than not that Kelley would have been deterred from carrying out the church shooting," the ruling stated.
"For these reasons, the government bears significant responsibility for the plaintiffs' harm."
Following this week's judgment, the families' lawyer said in a statement, "These families are the heroes here. While no amount can bring back the many lives lost or destroyed at the hands of the government's negligence, their bravery in obtaining this verdict will make this country safer by helping ensure that this type of governmental failure does not happen in our country again."
