WASHINGTON/NEW YORK — Cameras at 345 Park Avenue flagged an approaching gunman on Monday as a potential threat that required immediate attention, seconds before he burst into the office skyscraper’s lobby and began firing, according to two former federal officials familiar with New York building security systems.

A still frame of CCTV footage obtained by Reuters and timestamped 6:26:52 p.m. ET – just over a minute before police received the first emergency call about the mass shooting – shows a man holding an assault-style rifle at his side. A computer-generated bright yellow box around him in the image indicates the use of software that analyzes live video feeds for threats requiring instant action, the former federal officials said.

The details about the system, which have not previously been reported, raise questions about whether the gunman could have been thwarted before his attack, the officials said. Rudin Management, the real estate company that owns the tower, declined to comment on the camera system and whether it prompted any immediate actions from security staff.

Police have identified the shooter as Shane Tamura, 27, a Las Vegas resident with a history of mental illness. He killed two security officers, including a police officer working on a paid security detail, a Rudin employee and an investment firm executive before taking his own life.

The yellow box surrounding the shooter as he walked toward the entrance was meant to alert guards at the front security desk, the former officials said.

Michael Dorn, executive director of Safe Havens International, which advises schools on how to protect themselves from active shooters, said that even with such a video system in place, the threat still needs to be relayed to the building’s occupants immediately by the security staff.

“You can’t automate this away,” said Dorn, a former anti-terrorism adviser to the Georgia Department of Homeland Security and an expert on mass casualty events.

Security Experts Hit With Questions

Experts said some systems allow security guards to initiate an immediate lockdown of external doors, elevators and other access points.

Matthew Dumpert, global leader of enterprise security risk management at financial and risk advisory firm Kroll, said the attack – the city’s deadliest mass shooting in decades – prompted clients to call with questions about how to protect themselves from similar attacks. The reaction is reminiscent of the aftermath of the killing in December of United Healthcare executive Brian Thompson in Manhattan, when several companies enhanced executive protection in response.

“It takes significant resources, alarms to notify people, training to recognize it, physical security elements like locks to lock down facilities and prevent somebody from having free flow access through a facility,” Dumpert said.

Glen Kucera, president of Allied Universal, a global security firm, also was fielding calls from clients on Tuesday.

“The only way to have avoided this was to keep the shooter outside, which is very difficult,” Kucera said, adding it was clear the gunman intended to cause harm and not survive the encounter, which made him the most difficult kind of the threat to stop.

The security systems at 345 Park Avenue were typical of high-end offices in New York, according to Dave Komendat, senior security advisor at the risk mitigation firm International SOS.

While the lobby is open to the public, as in most buildings, visitors check in at security desks to access the elevators, which are behind turnstiles. Rudin’s offices, where the gunman killed himself, has bathrooms that doubled as bulletproof safe rooms, likely saving lives, Mayor Eric Adams said.

Numerous companies have implemented enhanced security for the rest of the week following the shooting, including additional guards, according to the Partnership for New York City, which represents more than 300 banks, investment firms and other companies in the city.

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(Reporting by Jana Winter and Jim Oliphant in Washington, and Sami Marshak, Saeed Azhar and Isla Binnie in New York; Writing and additional reporting by Joseph Ax; Editing by Donna Bryson, Scott Malone and Daniel Wallis)