A gunman armed with an assault rifle attacked a Manhattan skyscraper, killing four people before turning the weapon on himself.

The assailant, identified as 27-year-old Shane Tamura from Las Vegas, entered an office building on Park Avenue on Monday evening, firing shots in the lobby before heading to the 33rd floor to continue the rampage.

Among the victims was 36-year-old NYPD officer Didarul Islam, who was working security at the time. The identities of the three other fatalities have not yet been released.

Authorities say Tamura, who had a history of mental health struggles, drove cross-country from Las Vegas before the attack. Investigators are still determining a motive.

The shooting triggered panic as gunfire erupted around 6:30 p.m. ET (22:30 GMT), sending pedestrians scrambling for safety. Inside the building, terrified workers barricaded themselves in offices, stacking furniture against doors for protection.

The high-rise houses major organizations, including the NFL, financial firms like Blackstone and KPMG, and other corporate offices.

NYPD Commissioner Jessica Tisch confirmed the gunman acted alone and announced that a fifth victim was hospitalized in critical but stable condition.

Officer Islam, an immigrant from Bangladesh and a father of two with another child on the way, had served with the NYPD for three and a half years. Local leaders hailed him as a hero, with Commissioner Tisch stating, “He made the ultimate sacrifice.”

After shooting Islam at the entrance, Tamura targeted a woman hiding behind a pillar before indiscriminately firing across the lobby, striking multiple people, including a security guard. He then took an elevator upstairs, where he killed one more person before fatally shooting himself.

Police discovered additional ammunition and a revolver in Tamura’s double-parked car, registered in Nevada, where he legally owned firearms.

The attack disrupted Midtown Manhattan, halting traffic and public transit. Witnesses reported hearing gunfire, and law enforcement spent hours clearing the building floor by floor. Nearby, café worker Mama Bouhenni described seeing evacuees with their hands raised, many of whom she recognized as regular customers. “This is so terrifying for them,” she said. “I hope they can go home safe.”

Indrani Basu contributed to this report.