New York. A shooting at a midtown Manhattan office building on Monday left at least five people dead, including an off-duty New York City police officer, officials said.

Police identified the gunman as Shane Tamura of Las Vegas, who died by suicide at the scene. According to Police Commissioner Jessica Tisch, Tamura had a documented history of mental illness, but his motive remains unknown.

“We are working to understand why he targeted this particular location,” Tisch said during a press briefing.

Mayor Eric Adams said another man was seriously injured and remains in critical condition. “Five innocent people were shot, along with the perpetrator,” Adams said, adding that authorities are still “unraveling” the sequence of events.

The fallen officer, a 36-year-old immigrant from Bangladesh, had served with the NYPD for three and a half years. “He died as he lived. A hero,” Tisch said.

Surveillance footage showed Tamura exiting a double-parked BMW carrying an M4 rifle. He opened fire on the officer as he entered the building, then shot a woman who tried to take cover and continued “spraying” the lobby with gunfire, Tisch said. Tamura then moved toward the elevators, shooting a security guard hiding behind a desk and another man in the lobby.

Police later recovered a rifle case, a revolver, magazines, and additional ammunition from his vehicle.

Emergency services were called to the Park Avenue office tower at approximately 6:30 p.m., according to the Fire Department of New York. The building houses several major financial firms and the National Football League offices.

Jessica Chen, a witness, told ABC News she was attending a presentation on the second floor when she heard multiple shots from below. She and others barricaded themselves in a conference room using tables. “We were honestly really, really scared,” she said, recalling that she texted her parents to say she loved them.

Mayor Adams urged people still inside the building to shelter in place as officers conducted a floor-by-floor search. He later visited the hospital to meet with victims' families.

TV footage showed evacuations with people emerging from the building with their hands raised. The scene is located just north of Grand Central Terminal and a block from St. Patrick’s Cathedral, an area typically packed with commuters and tourists.

The city’s emergency alert system warned of road closures, transit disruptions, and heavy traffic in the area.

Despite the incident, New York City is on track to record its fewest murders and gun injuries in decades, according to recent NYPD data.