A knife-wielding grocery store employee attacked eight co-workers Friday, seriously injuring five before a witness pulled a gun and stopped him, police said.

The 21-year-old suspect, whose name was withheld pending charges, was arrested and then taken to a hospital after complaining of chest pains, Memphis Police Sgt. Vince Higgins said. The attack apparently stemmed from a work dispute, police said.

Five victims, one in critical condition, were admitted to the Regional Medical Center, the main trauma hospital for the Memphis area. Three others were less badly hurt and treated at another hospital.

The attacker, chasing one victim into the store's parking lot, was subdued by Chris Cope, manager of a financial services office in the same small shopping center, Higgins said.

Cope said he grabbed a 9mm semiautomatic pistol from his pickup truck when he saw the attacker chasing the victim "like something in a serial killer movie."

"When he turned around and saw my pistol, he threw the knife away, put his hands up and got on the ground," Cope told The Associated Press. "He saw my gun and that was pretty much it."

Police arrived within minutes and took the attacker into custody.

"He just kept saying, 'I'm insane. I wish I was never born' and that kind of stuff," Cope said.

The attack started in an employee area of the Schnucks supermarket on the outskirts of Memphis and no customers were involved, Higgins said.

Police said two large kitchen knives used in the attack were found at the scene.

Witness Frank Rector said the attacker held a knife high in a stabbing position as he chased a victim into the parking lot. The victim, Rector said, "was circling, trying to get away from him."

The ages of the victims were not immediately released. Higgins and a company spokeswoman said all the victims were employees of the store.

The spokeswoman said officials from the St. Louis-based company were on their way to the scene.

Higgins said police were pulling into the parking lot as Cope was confronting the attacker.

"We commend him," Higgins said. "But we don't encourage people to take that kind of risk. He could have been hurt."