WASHINGTON • A man dressed in a private security uniform made "some references to Allah" as he stabbed and wounded eight people in a shopping mall in Minnesota on Saturday night.
He was shot dead by an off-duty officer, police said.
The incident came after a pipe bomb exploded near a boardwalk in Seaside Park, New Jersey, shortly before hundreds of people were expected to run through the area in a charity race.
No injuries or damage to the surrounding buildings were reported and the area was immediately placed on lockdown, but the incident heightened fears of a terror attack.
The Minnesota mall suspect - whose identity has not been revealed - "asked at least one person if they were Muslim before he assaulted them", police chief Blair Anderson of the city of St Cloud, where the attack took place, told journalists.
But he emphasised that the assailant's motivation remained unclear and said "whether that was a terrorist attack or not, I'm not willing to say that right now because we just don't know".
Mr Anderson said the armed suspect entered the Crossroads Centre mall in St Cloud, a city of about 67,000 people about 110km north-west of Minneapolis, and attacked at least eight people.
The man had at least one knife and "made some references to Allah", the police chief said.
He said the eight people wounded were taken to hospital, where one is expected to remain.
The suspect had a history of minor traffic violations, Mr Anderson said, adding that the police do not have reason to believe the attack was connected to any other incident.
The St Cloud mall was put on lockdown in the aftermath of the attack, with local media reporting that people were being allowed to leave late on Saturday.
"It's an awful day," said Mr Anderson. "Starting tomorrow, things won't be the same here."