Klein Michael Thaxton (Facebook)

PITTSBURGH (AP) — An armed man with a military background took a hostage inside an upper floor of a downtown Pittsburgh office building on Friday and posted Facebook updates saying he’d “lost everything.”

Police Chief Nate Harper identified the hostage-taker as Klein Michael Thaxton, who wrote on Facebook that people will “never have to woryy (sic) about me again” after he took a man hostage inside a benefits administration firm on the 16th floor of Three Gateway Center.

Harper said Thaxton had been as cooperative, although he has made no demands.

“His demeanor right now is calm and he’s not being irrational,” said Harper, who had described the suspect as ex-military but declined to go into more detail.

Workers milled around near the building after they were ordered out shortly after 8 a.m. when employees in a nearby office called 911 to report an emergency at CW Breitsman Associates, a firm that runs employee-benefits programs.

Police brought the suspect’s mother to the office building, Harper said. She said she doesn’t know what drove her son to take a hostage, he said.

A worker on the 16th floor described a woman running into her office yelling for someone to call 911. Kathi Dvorak, an administrative assistant at AXA Advisors, said a second woman ran in and said her office was being robbed.

Joel Kirchartz, a 28-year-old web developer who works on the 17th floor, said he and his co-workers looked out the windows Friday morning and “a bunch of cops pulled up with all sorts of sirens going; there must have been 20 of them.” He said he went downstairs to find out what was happening and by the time he got outside, police had sealed the building.

Another worker, Sarah Vereb, said she was at her desk when she was ordered to leave the building shortly after a friend called to report that she wasn’t being allowed up from the lobby.

Hundreds of workers walked down the stairwell. Vereb said the exodus was orderly and “very, very quiet.”

A phone message left for the building’s Santa Monica, Calif.-based ownership group was not immediately returned. The building complex management office confirmed the evacuation and said it was working with police.

Copyright 2012 The Associated Press.