At least 10 people were killed in a mass shooting by a gunman wearing military-style gear — who possibly livestreamed the mayhem — at a Buffalo supermarket Saturday afternoon, law enforcement sources said.

The Buffalo Police Department tweeted at 3 p.m. that it was on the scene of a mass shooting at a Tops supermarket on Jefferson Avenue.

Police there said Saturday afternoon that the alleged shooter, who was not identified, was in custody.

As many as five bodies were found in the parking lot, the Buffalo News reported saying three people were wounded, two of them critically.

“Bullets and blood are everywhere,” a police source told the paper.

One of the dead was a recently retired Buffalo police officer who was working security at the store, the paper said. 

The shooter entered the market carrying a rifle and wearing military-style gear or a type of body armor, according to a report.

The store’s operation manager told the Buffalo News she thought she heard 70 shots.

She saw the shooter and said, “He looked like he was in the Army.”

The gunman may have been livestreaming the shooting, according to a police official who said authorities were investigating whether he posted a manifesto online.

Authorities said there was no clear motive for the carnage but were investigating whether it was racially motivated.

The market is located in a mostly black neighborhood about three miles north of downtown Buffalo.

Two people who saw the gunman leaving the store described him as a white man in his late teens or early 20s wearing camouflage attire with a black helmet.

“He was standing there with the gun to his chin. We were like what the heck is going on? Why does this kid have a gun to his face?” said witness Braedyn Kephart.

Kephart said the man dropped to his knees, ripped off his helmet and let go of his gun and then was tackled by police.

One regular shopper at the market told a local television station that he knew several of those killed.

“I lost three people today that I know and talk to five, six times a week. One, a friend of over 30 years, another a friend of 20 years. This is insane,” the man said.

The supermarket chain tweeted a statement saying it was “shocked and saddened by this senseless act of violence.”

Gov. Kathy Hochul tweeted that she was “closely monitoring the shooting at a grocery store in Buffalo,” her hometown. She said state officials have offered help to local authorities.

Attorney General Merrick Garland was said to have been briefed on the shooting.

With Post wires