Three people were killed and three others injured after a Halloween house party in a quiet Northglenn neighborhood turned deadly.

Shortly after midnight, police officers responded to reports of shots fired at a residence in the 200 block of Belford Drive.

When officers arrived, they discovered a large gathering with multiple people wounded by gunfire. A large Halloween house party had been taking place, witnesses said.

One person was pronounced dead at the scene, and five additional victims were transported to area hospitals, where two later died, according to James Burlison, spokesperson for the Northglenn Police Department.

Three others remain hospitalized with varying degrees of injuries.

No arrests were made Friday, police said.

Neighbors said the home is a rental property and describe it as a situation in which multiple tenants were crammed into the 1964 split-level home.

Kimberly Mopar, who lives across the street from the home, had just settled in Thursday night after taking her children trick or treating.

“Then I heard what I thought was fireworks about midnight,” she said. “And I thought, ‘Who’s setting off fireworks for Halloween?’ Then I heard the gunshots and people screaming.”

Authorities issued a shelter-in-place order, and Mopar said that, within minutes, the once-quiet street was flooded with police and emergency vehicles.

Mopar said the newest tenants moved in just a month ago.

Neighbors said it’s hard to know exactly how many people actually live in the house at any given time and that in the past month, there have been at least four police calls to the home.

Sara Vonfelt, who lives next door to the house, also heard the gunshots and estimated that somewhere between 15 and 20 rounds were fired.

Sharing her neighbors’ concerns about safety and domestic violence, Vonfelt said, in the past, she’d witnessed a man who was known to live in the home beating his girlfriend in the street.

“It’s just scary watching everything last night and then see the coroner here this morning, just makes your heart sink because, you know, it was kids,” she said.

Vonfelt speculated the age of the victims to be “teenagers,” as she saw one of them being loaded onto a stretcher.

“I think he was either deceased, or very close to it, because one of his friends or relatives dropped to their knees in front of the ambulance,” she said.

Vonfelt said she and many neighbors believe the incident was gang-related, as her children said they heard “gang chirps” or whistles that gang members are known to use to announce their presence.

Vonfelt’s daughter, who she asked not to be identified by name, said a few hours prior to the shooting, a man approached her and her brother asking for an address.

“So, like 9:30 last night, we came home from trick or treating, and we were walking in on the porch, and a guy was standing in front of the house on the sidewalk, and he was asking where a certain address was,” she said.

The family is planning to move, Vonfeldt said.

Law enforcement officials said at a brief press conference on Friday there are no suspects in custody and that there are no known active threats to the community.

Burlison reiterated that it’s an active inquiry and certain details couldn’t be shared as “they may jeopardize that investigation.”

“However,” he said, “we are pursuing leads in Northglenn and surrounding cities.”

Police said they believe there were multiple shooters involved and they are trying to identify the suspects.

The identities of the victims are being withheld pending notification of family members and autopsies. The information will be released by the Adams County Coroner’s Office.

Investigators ask anyone with information to contact police detectives at 303-450-8857.

Denver Gazette digital editor Jonathan Ingraham contributed to this report.