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.

Police arrested a 42-year-old man, Bradford James Gille, 42, of Afton, Mich., in the Saturday stabbings of 11 people in a Traverse City, Mich., Walmart.

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.