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.

© Jan-Michael Stump/Traverse City Record-Eagle, via Associated Press

One person was in custody after what the authorities said was a random attack at a store near Traverse City, Mich.

© Jan-Michael Stump/Traverse City Record-Eagle, via Associated Press