The images of the four-day siege at the Westgate Mall in Nairobi, Kenya, are from half a world away, but they hit painfully close to home in the United States, which has more than 800 regional shopping centers.
"It's a frenzy of communications when something like that happens," said Bud Bradley, a vice president with AlliedBarton Security Services, one of the largest suppliers of shopping mall security personnel with some 12,000 officers. He said his phone began lighting up with calls from clients soon after the Nairobi attack began on Sept. 21.
(Read more: Malls mulling security boosts after Nairobi attack)
"Our mall customers want to know what we're doing, have we disseminated information—awareness information, as much as intel as we possibly could," Bradley told CNBC.
Bradley said the Nairobi attack strikes a nerve among those charged with protecting what law enforcement officials call "soft targets"—places like shopping malls and hotels that offer easy access to the public.
"I think it's just a wake-up call. It's a reminder that it's a distinct possibility that this type of activity is going to continue."