In an ABC News exclusive, Derrick Perry recounts his confrontation and pulling his gun on the man accused of stabbing 11 people at a Michigan Walmart.

A Walmart employee was helping a customer check out when she heard a warning that someone in the store had a knife.

One of the men who authorities say helped take down a suspect who stabbed eleven people at a Walmart told NBC News about how he sprung into action. Marine veteran Matthew Kolakowski says he took off running after the suspect and rammed him with a grocery cart to prevent him from hurting more people.