CHICAGO_Electronic identification cards, surveillance cameras and metal detectors are fixtures in high-rise office buildings, but experts say with thousands of people whizzing through the revolving doors each day, it is impossible to guarantee workers' safety.
More than five years after the Sept. 11 terrorist attacks, security for high-rises is still a tricky balance of protecting workers and doing it without choking off commerce.
Even with all the security gizmos and gadgets, a lone gunman with a grudge against an attorney marched into Chicago's Citigroup Center last week and forced a security guard to take him to the 38th floor, bypassing turnstiles that require photo-ID cards. When he reached his destination, he killed three men and shot a woman in the foot before he was shot by police snipers.
"What can you do when someone is holding a gun on someone?" said David Hooks, spokesman for the Citigroup Center.
Chicago Police Superintendent Phil Cline says security should be up to high-rise tenants and that it is not practical to put a metal detector in the lobby of every building.
Security is not a one-size-fits-all proposition, and must include specific security threats, state and city requirements, and cost, said Santo Scribani, regional vice president for American Commercial Security Services, a Houston-based subsidiary of ABM Industries Inc.
"It's a tremendous balancing act, it's the same balancing act that law enforcement encounters," Scribani said.
Other high-tech options like palm print or retinal scans and facial recognition programs exist, but are not widely used because they are not cost-effective and the public is not comfortable using them, Scribani said.
High-profile targets, including the Empire State Building in New York and Chicago's Sears Tower have metal detectors or walk-through X-ray scanners in their lobbies.
Federal judges, U.S. attorneys and FBI agents at Chicago's 28-story Dirksen Federal Building downtown do not mind going through metal detectors because they understand the benefits of added security, said Deputy U.S. Marshal Mark Gregoline.
"Everybody in the building, everybody is affiliated with the federal government, and especially in this post-9-11 environment, you try to take steps to try to head things off at the pass. You can't plan for everything, but you try to," Gregoline said.
Sometimes office massacres force changes outside the building.
In 1993, a man with three semiautomatic guns rampaged through a law office on the 34th floor of 101 California St. in San Francisco, killing eight people and wounding six. Democratic Sen. Dianne Feinstein was so shocked that she pushed for - and got - a federal assault weapons ban that prohibited the manufacture and sale of military-style assault weapons from 1994 until the ban expired in 2004.
"These were people doing everyday jobs, in an everyday place. A place forever tainted by the bloodshed caused by one man and his assault weapons," Feinstein said.
Two of the biggest security improvements since Sept. 11 - an increased partnership between private security and local law enforcement, and well-researched evacuation plans - do not have anything to do with technology, said Ron Vukas, executive vice president of the Building Owners and Management Association Chicago, which represents more than 90 percent of commercial properties in the city.
The cost of protecting high-rises varies by property, depending on tenants, whether security is contracted out, where the building is located, and other factors, Vukas said.
Still, it's impossible to prepare for every scenario.
"Since 9-11 all buildings have increased security, but ... when someone is willing to give up their own life to get at someone else, I don't know how you stop that," he said.