At least 11 people were being treated for injuries at Munson Medical Center in Traverse City, said Megan Brown, the chief communications officer for Munson Healthcare, which runs Munson Medical Center. Six people were in critical condition and five people were in serious condition as of 9 p.m., she said.
The hospital was still assessing the victims’ injuries, Ms. Brown said. She did not describe the nature of the injuries.
A man who was not publicly identified, a 42-year-old Michigan resident, was in custody, officials said. A motive for the attack was not immediately known.
The man used a “standard folding-style knife” in the attack, Sheriff Michael D. Shea of Grand Traverse County said at a news conference on Saturday night. He acted alone, Sheriff Shea said.
“Citizen involvement” brought the attack to an end, Sheriff Shea said, declining to elaborate.
The attack began close to 4:45 p.m. at the store’s checkout area and the attacker was detained less than three minutes after the police arrived, Sheriff Shea said.
The victims included six men and five women, he said. Three people were undergoing surgery, he said. He did not know the status of the other victims.
“Based on the information we have at this time, it was random act,” he said. “The victims were not predetermined.”
A shopper described a scene of mayhem and confusion.
Julia Martell was in the canned vegetables aisle at Walmart when she heard screaming and saw a man with a knife running through the store’s pharmacy area, she said.
As the man moved through the store, he was shoving and stabbing people, she said. Then the man changed course and started running toward her.
She saw the knife in his hand — a knife with a blade about two inches long — and ran. The man didn’t follow her and instead turned back toward the store entrance, she said.
“If anything, him not following me kind of scared me more because then you had no idea where he was,” she said.
Ms. Martell, 30, said she saw three people with stab wounds as she evacuated the store, including a man on the floor in the store’s frozen food section. There was “blood everywhere,” she said.
A spokesman for Walmart said the violence at its store was “unacceptable” and expressed gratitude for the quick response by emergency workers. The company is working closely with local law enforcement during their investigation, the spokesman said.
The F.B.I. was responding to help the sheriff’s office, Dan Bongino, deputy director of the F.B.I., said on social media.
Alyce McFadden and Chris Loud contributed reporting.
