(CNN) A former employee opened fire Wednesday at a transportation center in Texas, killing one person before turning the gun on himself, the sheriff said.

The gunman had been terminated from his job at Knight Transportation in Katy, Texas, earlier Wednesday morning, Harris County Sheriff Ron Hickman told reporters.

He later returned to the business, this time armed with two guns, the sheriff said.

"He parked right outside the building and came straight in," Hickman said.

CNN Map

Authorities haven't identified the victim or the gunman, who also died. Investigators believe the shooting was a "retaliatory act," Hickman said, and they assume the person killed was a supervisor.

Read More