The armed man who held one person hostage on a 16th floor of a major office building in downtown Pittsburgh surrendered, police said on Friday.

The ex-military suspect was identified as Klein Michael Thaxton by the Associated Press. He surrendered before 2 p.m. The businessman he held hostage is unhurt, according to Police Chief Nathan Harper. 

USA Today reported the incident began around 8 a.m. Friday morning, when Thaxton, 22, entered the office of CW Breitsman Associates, a firm that runs employee-benefits programs.

He was carrying a package, and initially said he had explosives in it. 

The building was evacuated but Thaxton continued to hold one worker hostage.

The hostage was later identified as Charles Breitsman, the owner of CW Breitsman Associates, the AP reported.

Police spokeswoman Diane Richard said, "(Thaxton) is a sick young man and we do need to take measures to see he is taken care of as well," according to the AP.

Earlier, Harper told reporters negotiators were talking with Thaxton, and his mother was at the scene and had also made contact. 

"He is calm, he is not being irrational," Harper said. 

The New York Daily News reported the office is located on the 16th floor of Three Gateway Center, one of six office buildings that dominate the city skyline.

Harper described the suspect as "ex-military," but would not elaborate. He said no injuries had been reported and no shots had been fired.

A worker on the same floor said the hostage-taking unfolded as people were arriving for work and left many people frightened and shocked.

Kathi Dvorak, an administrative assistant at AXA Advisors, said a woman ran into her office yelling for someone to call 911, and another said her office was being robbed.