Charles McKnight, 27, has been charged with first-degree murder and two counts of attempted first-degree murder, according to officials.
McKnight had been working with a temporary employment agency and had only been assigned to the WeatherTech facility since June 9.
Police said McKnight allegedly robbed some of his co-workers at gunpoint and when he was later confronted, he pulled out a gun and began firing.
Central Hightower, 37 from Plainfield, was killed. A 25-year-old man, who police say was one of the earlier robbery victims, is in critical condition. A third victim, a 43-year-old man, has been released from the hospital. All three were WeatherTech employees.