A disgruntled employee opened fire Monday at the Northrop Grumman Ships Systems (search) shipyard, critically wounding two co-workers, police said. The suspect was in custody.

Police Lt. Paul Leonard identified the alleged shooter as Alexander L. Lett (search), 41, of Moss Point, a 20-year employee of the large complex that builds ships for the Navy and the Coast Guard.

Lett tried to leave the building following the shooting but was detained by other Northrop employees, police said. Lett had arrived at work and "was disgruntled for some reason," Detective Sgt. Jeff Barnes said.

Singing River Hospital Systems (search) spokesman Richard Lucas said the wounded workers were in critical condition and had undergone surgery. They were both believed to be managers, officials said.

A 9 mm semiautomatic pistol was used in the shooting, Leonard said. He had no detail on how it was brought into the building.

In a statement, Northrop Grumman said company officials were "in close contact with the employees' families for support and assistance" but offered no additional details on the shooting. Northrop Grumman Ship Systems is Mississippi's largest private employer, with more than 12,000 workers.