St. Louis ? A disgruntled worker embroiled in a pension dispute with his company showed up at the plant and opened fire Thursday, killing three people and wounding five before apparently killing himself.

The shooting spree at ABB Group’s plant sent frightened co-workers scrambling into closets and to the snow-covered roof for safety.

Police declined to name the gunman, but media widely identified him as 51-year-old Timothy Hendron of Webster Groves, a St. Louis suburb. A fire official confirmed earlier Thursday that that was the name of the person police said they were seeking.

Police said a man believed to be the gunman was found dead inside the plant from an apparent self-inflicted gunshot wound.

“We’re very confident that this is the shooter,” Police Chief Dan Isom said at a news conference.

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