A gunman killed at least five people including himself at an office tower that houses Blackstone Inc’s global headquarters and the National Football League among others, sparking hours of chaos and fear in Midtown Manhattan on Monday evening.

Several others were injured in the attack at 345 Park Avenue, according to city officials. Those killed include at least one police officer. At least two people died at the tower, with the gunman’s body found on the 33rd floor. That floor is occupied by real estate firm Rudin Management.

Blackstone staffers work just below, where they pushed furniture in front of doors to barricade themselves in during the attack, employees said.

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The incident set off a chaotic scene in Midtown Manhattan, with scores of police cars cordoning off the area and a helicopter overhead. A man had been seen entering the skyscraper with a bulletproof vest and an assault rifle, according to the New York Post.

Across Wall Street, employees at other private equity firms and banks said they had swapped worried text messages and photos with their friends at Blackstone. One Blackstone employee shared a photo that showed couches piled close to the ceiling as a barricade. Two of the firm’s employees told friends they were hiding in the office pantries, according to people who received the messages.

When Blackstone’s offices later evacuated, some stayed behind, reluctant to go outside. Representatives for the company and the NFL had no immediate comment or didn’t respond to messages. Blackstone is the world’s largest alternative asset manager and employed almost 5,000 people at the end of last year.

Tenants of the building also include KPMG, which sent out a message to staff. Jefferies Financial Group Inc and Citadel, which both have locations nearby, went into lockdown.