After nearly a dozen people were stabbed at a Walmart in Traverse City, Michigan, Saturday afternoon, the quick actions of a couple of Marines and other bystanders helped stop the attacker from causing further harm.

The authorities on Sunday said that a motive for the attack, which left 11 people injured, remained unknown. Citizens, including one who was armed, helped to apprehend the suspect, officials said.

Authorities in Michigan say a man entered a Walmart in Traverse City on Saturday afternoon armed with a folding knife and stabbed 11 people before being stopped by shoppers and a sheriff's deputy. The attack began unfolding at 4:43 p.m., the Grand Traverse Sheriff's Office said in a statement posted online.