MOUNT PLEASANT -- A young Walmart employee described as popular and outgoing was stabbed to death at work Wednesday afternoon, causing police to close the bustling store for several hours.

David "D.J." Moultrie, 20, of Mount Pleasant, was stabbed while in an altercation with another man in front of the Food Center entrance at the Walmart Supercenter in The Market at Oakland on U.S. Highway 17, authorities said.

"Our thoughts and prayers go out to David's family and friends," said Dianna Gee, a Wal-Mart spokeswoman. "Employees are definitely mourning the loss. We all are. Associates are like family to Wal-Mart."

The incident took place shortly after 3 p.m., Mount Pleasant police Capt. Stan Gragg said. According to witnesses, the two men got into an argument, he said. One of them pulled out a sharp object and stabbed the other. The victim stumbled into the store and collapsed near the Food Center entrance, Gragg said.

Police have an 18-year-old suspect in custody. Darius Green of Rachel Cook Way in Awendaw was being questioned at the police department, Gragg said. As of 9:30 p.m. Green had not yet been taken to the county jail.

Asked about a motive, Gragg said he could not provide further details. There were unverified reports that the two men were arguing over a woman.

Police cleared the store of customers for several hours after the stabbing. For hours, yellow crime-scene tape barred customers from entering the usually busy store. By 7 p.m., workers were opening the entrances and allowing customers back in.

An employee who asked not to be identified said it was difficult reopening for business after having lost a co-worker. "We're trying to get thing back to normal," the man said.

Gee talked with a number of people at the store about Moultrie. "He was known as an upbeat, friendly, likable young man," she said. "He was really outgoing."

Moultrie had been with Walmart since December and was a cart-pusher, she said.

Walmart has been in touch with Moultrie's family and planned to have counselors at the store today to help associates deal with what happened, Gee said.

The store is near the intersection of U.S. 17 and Porcher's Bluff Road in northern Mount Pleasant.

Published reports that shots were fired inside the store were incorrect, Gragg said. A shelving unit fell to the floor, making a sound so loud people mistook it for gunfire, he said. The fallen shelf had nothing to do with the stabbing.