ST. LOUIS — The man suspected in a St. Louis workplace shooting that left four people dead and five injured Thursday is believed to be among the dead.

Fire officials identified the shooter as 51-year-old Timothy Hendron of Webster Groves. Police would not release his name but said a man believed to be the gunman was found dead inside ABB Group's plant from an apparent self-inflicted gunshot wound.

The shooting began at 6:30 a.m. Thursday at the plant where the Swiss-owned company makes electrical transformers. Police spent hours inside the sprawling plant searching for the gunman and additional victims.

The motive for the shooting isn't clear, but Hendron was among employees of the plant who sued ABB over its retirement benefits. The trial began Tuesday in Kansas City, Mo.