Police waged an hours-long gunfight with two men armed with high-powered rifles on Tuesday in and around a New Jersey cemetery and kosher market, leaving six people dead, including one officer and both suspects, authorities said.

The violence began after noon in the heart of Jersey City, the state’s second-largest municipality, directly across the Hudson River from Lower Manhattan, prompting a lock down of all Jersey City schools as law enforcement swarmed the area.

Police arriving on the scene immediately came under “high-powered rifle fire,” Jersey City Police Chief Michael Kelly told reporters.

While the gunmen’s motives were not known, there was no immediate evidence the bloodshed was either a hate crime or terror-related, Kelly said, adding, “but that’s certainly on the table.”

Investigators believe the two suspects, who were not yet identified, acted alone, officials said.

“Based on what we now know, there are no ongoing threats to public safety that have any connections to today’s events,”Governor Phil Murphy said at a separate news conference.

“This has been an incredibly tough day for Jersey City and the entire state of New Jersey.”

The two gunmen and three victims believed to be bystanders were pronounced dead inside the JC Kosher Supermarket. The slain police detective was fatally wounded near a cemetery about a mile away where the shooting apparently started when he tried to intercept one of the suspects, Kelly said

Kelly said he believed the civilians and the detective were all struck by gunfire from the suspects, who arrived in a stolen U-Haul truck and held police at bay around the store for hours before the shooting ended.

“Their movement was rapid and continuous for four hours within that area,” the chief said at an news briefing. He described the crime scene as “very extensive,” encompassing at least three locations. Hundreds of rounds were fired, he said.