On any given day, over 28,000 employees file into Lehman Brothers' 61 worldwide offices and sit down to work at their desks.

Many of them spent Monday morning cleaning them out.

“It's more devastating than I care to discuss," said one employee, who declined to give his name as he walked outside the investment firm's midtown Manhattan headquarters, carrying a shopping bag stuffed with paintings that once hung in his office.

“There's a lot of anger and feelings of uncertainty," he said. "It's not just about losing a job. I'll find another one. I've worked here for over 15 years and had a lot of wealth invested in this firm."

While no layoffs were officially announced, Lehman Brothers filed the largest bankruptcy in U.S. history on Monday, valued at $639 billion. The 158-year-old investment firm — smothered by the credit crisis and falling real estate values — filed for Chapter 11 protection to keep creditors at bay while it figures out how to restructure itself. The firm's last hope of surviving outside of court protection faded Sunday after British bank Barclays PLC withdrew its bid to buy the investment bank.

The bankruptcy filing marks the end of a Wall Street firm that started the U.S. cotton trade before the Civil War and financed the railroads that built a nation.

"It's sad and shocking," said a former Lehman Brothers equity research associate, who worked for the firm from 2001 to 2006 and declined to give his name. "This is one of the oldest financial institutions and every kid's dream after graduating from the Ivy league. It's very difficult to accept," he said.

But many employees — though angered — said they did not blame the federal government for its refusal to rescue the investment giant from bankruptcy.

"Do I think it's unfair the government hasn't rescued us as they did Bear Stearns and Freddie Mac and Fanny Mae? No, not at all," said Alan Miles, a Lehman employee. "About 70 percent of us in there are liberal Democrats, but we believe in capitalist markets and therefore I do not blame the government," he said.

Another employee — who identified himseld only as "Eli" — said the crisis is "much larger than just the U.S. economy."

"I don’t think that President Bush or either U.S. presidential candidate can do much about it," he said. "This will require major global economic turnaround."

Eli — who said he'd worked in Lehman Brothers' fixed income division for two years — told FOXNews.com that he heard about the bankruptcy filing after watching the news.

"As of Monday morning, no official statement had been sent out to us," he said. "We were just told to come into work to conduct business as usual."

Eli described his coworkers are "shocked and saddened" by the firm's collapse, but "keeping a smiling face by laughing and joking."

"We're all exchanging contact information so we can stay in touch and be there for each other," he said.

"There's a lot of joking going inside this building this morning," added another employee. "We don't know where we'll go from here, but we're doing our best to stay strong."

The Associated Press contributed to this report.