At least 11 people are being treated after a mass stabbing at Walmart in Traverse City on Saturday, July 26, and a suspect is in custody, local authorities said. Munson Healthcare in northern Michigan confirmed that "11 victims are being treated at Munson Medical Center" in connection to the incident. Six are in critical condition and five others are serious. Three required surgery. "As a result, our Emergency Department is currently experiencing a higher-than-usual volume of patients," it said. The Grand Traverse County Sheriff's Office is telling people to "please avoid the area as the investigation is ongoing." The FBI is also responding "to provide any necessary support," said Deputy Director Dan Bongino. Here's everything we know. The suspect, a 42-year-old Michigan resident, was subdued by bystanders at the store after he stabbed 11 people with a folding knife near a checkout counter, Grand Traverse County Sheriff Michael Shea said in a press conference Saturday evening. Shea said the actions by the suspect seemed to be random and the victims did not seem to be predetermined. He said the ages of the victims are unknown, and none of the victims seemed to be Walmart employees. The Michigan State Police crime lab is in route to processing the scene. Walmart will be closed until authorities complete investigating the scene, Shea said. Asked for advice in how to respond to this type of incident, Shea said to “be vigilant. Know that no area is immune to this kind of activity, unfortunately. If you see something, please reach out. Call 9-1-1." At around 8 p.m., more than 10 police cars sat in the parking lot of the Walmart, located in a strip mall south of downtown Traverse City. Cars and pedestrians could access other locations while the Walmart was blocked off. Carrie Kidd, an employee at HomeGoods two stores down from Walmart, said she was working the register when people exiting Walmart started flooding the store’s parking lot, which is adjoined with Walmart's, around 5 p.m. She said it didn’t feel scary, but did feel “chaotic.” “We didn’t know much. There was a lot of speculation,” she said. She said the store was slower than usual after the incident, and people couldn’t get in or out of the Crossing Circle area, where the stores are located, for a period after the incident. Michigan Gov. Gretchen Whitmer said in a social media post that she is "in touch with law enforcement about the horrible news out of Traverse City." "Our thoughts are with the victims and the community reeling from this brutal act of violence. I am grateful to the first responders for their swift response to apprehend the suspect," Whitmer said. Whitmer said she will "continue monitoring the situation closely." Former U.S. Transportation Secretary Pete Buttigieg, who owns a home in Traverse City, also posted to social media: "Along with the whole Traverse City community, Chasten and I are shaken by the awful and senseless violence at Walmart earlier today. We’re thinking of everyone affected and hoping and praying for speedy recovery for all those who were injured." Walmart issued an additional statement saying the retailer would work closely with law enforcement during 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," Joe Pennington, Walmart spokesperson, told USA TODAY. Pennington said the retail giant will "continue working closely with law enforcement during their investigation.” Traverse City, which the U.S. Census Bureau reports has a population of nearly 16,000, is in northern Michigan, about 150 miles north of Grand Rapids and 255 miles northwest of Detroit. Jonathan Limehouse and Bart Jansen of USA TODAY contributed. This is a developing story.