Six people are dead, including a New Jersey detective, after two suspects opened fire at a kosher market in Jersey City on Tuesday afternoon, police said.

Jersey City Police Chief Michael Kelly said one officer, three bystanders, and the two suspected gunman were all killed in an intense gun battle that lasted for hours in the Greenville neighborhood.

The shooting began at Bay View Cemetery, where 39-year-old Detective Joseph Seals was found dead, and then continued at JC Kosher Supermarket on Martin Luther King Drive, where the rest of the victims were found.

“We believe two of them are bad guys. We believe three of them are not. They may be civilians. Once again, this is all preliminary information,” Kelly said.

Heavy gunfire could be heard for over an hour after the two suspects barricaded themselves inside the supermarket. Authorities from multiple law enforcement agencies—including ATF and the FBI—swarmed the building, which is about eight miles from New York City, engaging in a long standoff with the suspects that began around 12:30 p.m.

“Our officers were under fire for hours,” Kelly said.

The Hudson County prosecutor’s office tweeted that two cops and a bystander had also been wounded. Kelly said the officers were taken to a local hospital and have since been released.

“I have been briefed on the unfolding situation in Jersey City. Our thoughts and prayers are with the men and women of the Jersey City Police Department, especially with the officers shot during this standoff, and with the residents and schoolchildren currently under lockdown,” Gov. Phil Murphy tweeted.

Kelly confirmed on Tuesday that officers are examining a stolen U-Haul truck “that may contain an incendiary device,” but did not provide any additional detail.

At the time, Department of Public Safety Director James Shea said there is “no indication of terrorism” in the shooting. Later Tuesday evening, Jersey City Mayor Steven Fulop tweeted that officials believed the “active shooters targeted the location they attacked” based on findings in an initial and ongoing investigation.

“Due to an excess of caution the community may see additional police resources in the days/weeks ahead. We have no indication there are any further threats,” Fulop wrote.

In several videos posted online, loud volleys of gunfire could be heard as bystanders pressed against a police-tape barrier. One video showed a line of police officers armed with weapons and protective gear walking down the sidewalk in a single line. In another, police guided several people away from the scene.

“I got caught in a one way street with a bunch of cars and I was wondering why nobody was moving. And all of a sudden I heard it. All the shots started. Shots started ringing out. When I heard it, I see people running. I got out of the car and I see cops ducked down, and cops getting out of the way,” Brian Clark, who witnessed the shooting, told CBS New York.

Andy Patel, who works at a liquor store about three blocks away from the incident, told the Associated Press he heard consistent gunfire fire for about an hour on Tuesday.

“I can hear the gunshots. It’s like firecrackers going off. They were shooting like crazy about an hour ago. Then it stopped for like 20 or 30 minutes. The cops were clearing everyone off the streets,” Patel said.

The School District of Jersey City said at least 10 schools were locked down Tuesday “due to police activity,” but that all students and faculty are safe. The NJ Transit Police tweeted several New Jersey transit rail lines have been “suspended” until further notice.