In New York City, in New York state, a place with some of America’s most stringent gun laws, and a police force that dwarfs the armies of most countries in manpower, a gunman was able to enter one of the city’s most secure office buildings and kill four people and wound others. How did that happen? Now, reports The WSJ, offices are reevaluating security. Chip Cutter writes:

Securing corporate offices in a dense urban setting such as Manhattan can be particularly difficult. Unlike suburban office parks or other corporate facilities, where individuals might be stopped at a guard station far from a building, companies in a city can do only so much to restrict guests coming and going from a lobby.

Many companies already monitor for threats online, conduct annual safety training with workers and encourage colleagues to speak up if they see something suspicious. But once a suspect takes down lobby security staff, as happened on Monday, it becomes easier to access the office floors.

Some companies are beginning to install artificial-intelligence-enhanced video surveillance software to look for anyone who appears to have a weapon. Such systems can then immediately trigger a building to go into lockdown mode or for staffers to disable elevator service, Stephens said.

The idea is that, “even if he does get inside, he’s not going anywhere within the tower,” Stephens said. Such technology can be expensive and is still evolving, though. “I certainly wouldn’t call it commonplace,” he said.