Two teenagers were killed and at least 14 others injured following a mass shooting at a backyard party in Rochester, New York, early Saturday, according to the Rochester Police Department.
The shooting took place on Pennsylvania Avenue around 12:25 a.m. ET, according to authorities. At least 40 rounds were fired, police said.
This is "truly a tragedy of epic proportions," Rochester interim Police Chief Mark Simmons said during a press conference early Saturday morning. "Sixteen victims is unheard of."
The two deceased victims were identified by police as Jarvis Alexander and Jaquayla Young, both 19. They were pronounced dead at the scene, Capt. Frank Umbrino said during a press briefing later on Saturday.
The 14 surviving victims ranged in age from 17 to 23 and were taken to two local hospitals, police said. None of the other victims have suffered life-threatening injuries, police said.
At least three or four people fired, Umbrino said, with the gunfight lasting for over a minute. The altercation likely started in the front of the house, he said, with shots fired in the front, back and up the street. Casings were found in a two- to three-block span, the captain said.
"Jaquayla and Jarvis were likely not the intended targets," Umbrino said. "We have two innocent victims here who were attending a party with a few friends."
Police have not identified any suspects.
Officers are still interviewing witnesses to get more information about how the shooting started and learn more about the suspects, as well as going through video evidence, police said.
"It's going to be a very tedious and long process," Umbrino said. "We need people to come forward and give us what we need to hold those responsible."
It is unclear what precipitated the shooting, Umbrino said, though it appears that an argument "quickly escalated."
The house party had started small, but grew to upward of 200 people when attendees of two different parties in the neighborhood "started to infiltrate the party where this occurred," Umbrino said.
A witness told Rochester ABC affiliate WHAM that the gunfire sounded "like the Vietnam War."
When police arrived at the scene, Simmons said officers saw 100 people running to and from the location. Two people fleeing the scene were also injured. Up until the 911 call came in for the shooting, there were no calls to complain about the large gathering, he said.
"This tragic act of violence has impacted many people's lives and families," Rochester Mayor Lovely Warren said in a statement provided to WHAM Saturday. "I'm begging everyone to remain calm and exercise deep restraint as RPD investigates what happened here and seeks those responsible."
The city of Rochester has been on edge recently with nightly protests following the release of footage that showed the death of 41-year-old Daniel Prude in police custody.
In the video, officers are seen pinning Prude to the ground while a spit bag is on his head, and he eventually appears to go unconscious. Prude died a week later. The Monroe County medical examiner listed his death as a homicide caused by "complications of asphyxia in the setting of physical restraint."
Warren fired Police Chief La'Ron Singletary on Monday.
ABC News' Ivan Pereira contributed to this report.