A demoted employee at a Chicago tech company has critically wounded his CEO and killed himself in a shock shooting inside his high-rise office building.

Arrowstream CEO Steven LaVoie, 54, is in critical condition in hospital after the unnamed employee met him one-on-one on the 17th floor to shoot him.

After a short struggle, the 59-year-old employee managed to shoot Mr LaVoie twice before turning the gun on himself, NBC News reports.

According to Chicago Police Superintendent Garry McCarthy, the company had been downsizing and the alleged shooter, a long-time employee of Arrowstream, was a part of a group of people who were demoted.