ST. PAUL, Minn. (AP) — Thousands of law enforcement officers, firefighters and paramedics are expected to pack a Minnesota church on Wednesday for a memorial service for three first responders who were gunned down while responding to a report of a domestic incident at a home with seven children inside.

The Minneapolis suburb of Burnsville has been in mourning in the week and a half since police Officers Paul Elmstrand and Matthew Ruge, both 27, and firefighter-paramedic Adam Finseth, 40, were slain. Investigators say Shannon Gooden, 38, opened fire on them without warning during a standoff at his home, then later killed himself.

“On February 18th, our worlds were completely shattered. It was the darkest day in our police and fire department history. And it is still nearly impossible for us to comprehend,” Burnsville Police Chief Tanya Schwartz said at a briefing on service arrangements Monday, as she thanked the community for its outpouring of support.

The service will be at the nondenominational Grace Church in suburban Eden Prairie, one of the largest churches in the Minneapolis area. Because of the overflow crowd expected there, officials have encouraged the public to instead watch the livestream from home or at Prince of Peace Lutheran Church in Burnsville. The livestream will be viewable on the Grace Church website and its YouTube channel.

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A procession of public safety vehicles will head from the Eden Prairie church after the service to Burnsville, where it will pass a fire station, police headquarters and the Burnsville church. Officials encouraged people to line the route to pay their respects.

“So much of this memorial service will be like nothing Minnesota has ever seen,” Minnesota Department of Public Safety spokesperson Howie Padilla told reporters, citing the expected attendance of not only law enforcement officers but firefighters and paramedics as well.

Authorities have made only limited information about the incident public, citing the ongoing investigation.

According to the Minnesota Bureau of Criminal Apprehension, which is leading the investigation, police were dispatched to the home around 1:50 a.m. Sunday, Feb. 18. 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 BCA says, Gooden opened fire on officers inside without warning.

The BCA said Elmstrand and Ruge, and Sgt. Adam Medlicott, 38, are believed to have been first shot inside the home. 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 BCA. 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. Medlicott survived and is recovering at home.

The BCA said Gooden had “several firearms” and shot more than 100 rounds before killing himself. A court document filed by a BCA agent said the initial 911 call was “regarding an alleged sexual assault allegation.” Authorities have not provided further details about that.

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.