The deadly assault on a luxury Nairobi mall Saturday has raised concerns about security at shopping centers amid fears of copycat violence or other terror attacks, industry officials and other experts tell NBC News. As Kenyan forces struggled to take control of the Westgate mall on the third day of the horrifying attack, U.S. shopping center firms are considering ramping up security measures at thousands of malls across the country. “There’s going to be a response,” said Malachy Kavanagh of the International Council of Shopping Centers, a U.S.-based trade group of mall and shopping center owners.