At least 11 people were stabbed at a Walmart in Traverse City, with six people in a critical condition, Michigan authorities said.

About 4.45pm on Saturday, a 42-year-old man allegedly entered the store and used a folding knife to stab 11 people, the Grand Traverse county sheriff’s office said, adding that it appeared to have been a random act of violence.

A sheriff’s deputy arrived within minutes and took the man into custody. People in the store helped apprehend the suspect and treat victims, the sheriff’s office said.

Emergency vehicles and uniformed first responders gathered in the parking lot of the shopping centre, which houses several other retail stores.

Authorities also were seen interviewing employees, still wearing blue uniform vests and name tags, as the response gave way to an investigation.

Tiffany DeFell, 36, who lives in Honor, about 25 miles (40km) from Traverse City, said she was in the store’s parking lot when she saw chaos erupt around her.

“It was really scary. Me and my sister were just freaking out,” she said.

Munson Healthcare said via social media that 11 people were being treated at the region’s largest hospital in northern Michigan. A spokesperson said six people were critical and five were in serious condition late on Saturday.

The hospital requested patience and understanding from the public as “our emergency department is currently experiencing a higher than usual volume of patients”.

Shea said the weapon involved appeared to be a folding knife. The suspect in custody was believed to be a Michigan resident.

The Michigan governor, Gretchen Whitmer, posted on social media that she was aware of the incident and in touch with law enforcement.

“Our thoughts are with the victims and the community reeling from this brutal act of violence,” she said. “I am grateful to the first responders for their swift response to apprehend the suspect.”

Walmart said it would continue to work closely with law enforcement in the investigation. “Violence like this is unacceptable. Our thoughts are with those who were injured and we’re thankful for the swift action of first responders,” a statement said.

Traverse City is about 255 miles (410km) north-west of Detroit and is a popular holiday spot on the coast of Lake Michigan.