A gunman wearing a rifle and body armor opened fire at a supermarket in Buffalo, New York, killing at least 10 people before being arrested.
Details of the number of additional people slaughtered at Tops Friendly Market today and their conditions were not immediately available.
Two officials who spoke to The Associated Press were not authorized to speak publicly on the matter and did so on condition of anonymity.
Investigators believe the man may have livestreamed the shooting and was investigating whether he had posted a manifesto online, the official said.
The official warned that the investigation was still in its early stages and that authorities had not yet discerned a clear motive, but were investigating whether the shooting was racially motivated.
The supermarket is in a predominantly black neighborhood about 3 miles north of downtown Buffalo.
The surrounding area is mostly residential, with a Family Dollar store and a fire station near the store.
Buffalo police confirmed the shooter was in custody in a tweet, but did not identify the suspect.
Witnesses reported that the shooter was wearing military-style clothing in addition to the bulletproof vest, one of the officials said.
Braedyn Kephart and Shane Hill, both 20, pulled into the parking lot just as the shooter exited.
They described him as a white male in his late teens or early twenties wearing full camouflage, a black helmet, and what appeared to be a rifle.
“He was standing there with the gun to his chin. We were like what was going on? Why does this kid have a gun to his face?” Kephart said.
“He ripped off his helmet, dropped his gun and was tackled by the police.”
Police sealed off the block, lined with onlookers, and yellow police surrounded the full parking lot