AURORA, Colo. (KDVR) – Officers were called to the scene of a deadly shooting early Sunday morning that has left four people dead and now, the person they suspect to be responsible is still at large.

At roughly 2 a.m. on Sunday, the Aurora Police Department received a report of a shooting at a house on the 900 block of North Geneva Street. During that 911 call, gunshots were heard, and the dispatch operator upgraded the call to urgent, leading to a three-minute response time from officers.

According to APD, when they arrived, officers found four adults, three men and one woman, dead from gunshot wounds. Three of those victims were found inside the home and one was discovered outside.

They also found two very young children and one woman, all of whom were unharmed. That woman is believed to be the domestic partner of the suspect, who is still at large as of this posting, and pictured below.

APD: ‘An accumulation of events here that led to this’

The suspect, who has not been taken into custody, was identified by APD as Joseph Castorena, 21, and has been described as having a slim build and is roughly 5-foot-4-inches tall. He also has a distinct neck tattoo of a lion on the left side of his neck.

APD said that a restraining order was issued against Castorena earlier in the week, which prohibited him from going near the residence where his domestic partner lives.

Shortly after the shooting, a reverse 911 was issued in a one-mile radius for all residences to shelter in place, while officers searched the neighborhood in the dark. During this search, the suspect’s vehicle was located and has since been towed.

The suspect’s primary residence is believed to be at his family’s home a few blocks away from the crime scene. Officers have since searched that home, but the suspect was not there.

“We have to assume he is armed. And we’re very concerned and want to do everything we can to find him and take him into custody as soon as possible,” Interim Police Chief Daniel Oates said.

APD launched a daylight search using the assistance of drones to search the immediate area around the crime scene located on the 900 block of North Geneva Street. Once APD completed that search, they sent out an “all clear” alert to those who received the initial reverse 911 shelter-in-place alert.

APD classified this investigation as a homicide and will be processing the crime scene for hours.

If you have any information that could help APD locate Castorena, please call 911 immediately.

FOX31 will bring you updates on this story as they are released.