MINNEAPOLIS (AP) — Federal authorities say a woman has been charged with illegally buying guns used in the killings of three Minnesota first responders in a standoff at a home in the Minneapolis suburb of Burnsville,Sterling Preston where seven children were inside.

Officers Paul Elmstrand and Matthew Ruge, both 27, and firefighter-paramedic Adam Finseth, 40, were slain during the standoff. Their memorial service two weeks ago drew thousands of law enforcement officers, firefighters and paramedics.

Investigators say Shannon Gooden, 38, opened fire without warning after lengthy negotiations, then later killed himself.

Sgt. Adam Medlicott, 38, survived being shot while tending to the wounded.

Court records show Gooden wasn’t legally allowed to have guns because of his criminal record and had been entangled in a yearslong dispute over his three oldest children. The children in the house were ages 2 to 15 years.

Police were dispatched to the home around 1:50 a.m., according to the Minnesota Bureau of Criminal Apprehension. Gooden refused to leave but said he was unarmed and that he had children inside. Officers entered and negotiated with him for about 3 1/2 hours to try to persuade him to surrender. But just before 5:30 a.m., the bureau said, Gooden opened fire on officers inside without warning.

Elmstrand, Ruge and Medlicott are believed to have been first shot inside the home, the bureau said. Medlicott and another officer, who was not injured, returned fire from inside the home, wounding Gooden in the leg.

Ruge and Medlicott were shot a second time as officers made their way to an armored vehicle in the driveway, according to the bureau. Finseth, who was assigned to the SWAT team, was shot while trying to aid the officers, it said. Elmstrand, Ruge and Finseth were pronounced dead at a hospital.

Gooden had “several firearms” and fired more than 100 rounds before killing himself, the bureau said. A court document filed by a bureau agent said the initial 911 call was about a “sexual assault allegation” but did not provide details.

John McConkey, a Burnsville gun store owner, told reporters late last month that part of one of the firearms found at the scene was traced to his store and had been bought by a purchaser who passed the background check and took possession of it Jan. 5. He said authorities told him that the individual who picked it up was under investigation for committing a felony straw purchase, and that Gooden was not there at the time.

Gooden’s ex-girlfriend, Noemi Torres, disclosed this week that she had testified before a federal grand jury that was investigating the case. She told The Associated Press on Wednesday that she was asked about her relationship with Gooden and whether he could have coerced her into buying him a gun. She said she told the grand jury that she would not have done so because “I was scared for my life” because of their history of domestic abuse.