A man carrying a rifle killed four people at a New York City office tower Monday, including an off-duty New York City police officer, and wounded a fifth before taking his own life, officials said. The officer who was killed was Didarul Islam, 36, an immigrant from Bangladesh who had served as a police officer in New York City for 3 1/2 years. “He died as he lived. A hero,” police Commissioner Jessica Tisch said at a news conference. He was married with two young boys, and his wife is pregnant with their third child, she said. Police identified the gunman as Shane Tamura, of Las Vegas, and said he killed himself. He had a ‘documented mental health history,’ but the motive is still unknown, Tisch said. “We are working to understand why he targeted this particular location,” Tisch said. Another man was seriously injured and remains in critical condition, Mayor Eric Adams said. Adams said officials are still “unraveling” what took place. “Five innocent people were shot” along with the perpetrator, he said. Surveillance video showed a man exiting a double parked BMW and carrying an M4 rifle before he walks toward the building. He immediately opened fire on the NYPD officer as he entered the building and shot a woman who tried to take cover and then began “spraying” the lobby with gunfire, Tisch said. The man then made his way to the elevator bank and shot a security guard who was taking cover behind a security desk and shot another man in the lobby, the commissioner said. The man took the elevator to the 33rd floor to a real estate management company and one person was shot and killed on the floor. The man then walks down a hallway and shot himself, the commissioner said. Officers found a rifle case, a revolver, magazines and ammunition in his car, Tisch said. The Fire Department of New York said emergency crews were called to the Park Avenue office building around 6:30 p.m. for a report of someone shot. The building houses some of the country’s top financial firms and the National Football League. Jessica Chen told ABC News she was watching a presentation with dozens of other people on the second floor when she “heard multiple shots go off in quick succession from the first floor.” She and others ran into a conference room and barricaded tables against the door. “We were honestly really, really scared,” she said, adding that she texted her parents to tell them that she loves them. Local TV footage showed lines of people evacuating the office building with their hands above their heads. The building includes offices of Blackstone and the consulate general of Ireland. Tisch says she believes there were two officers working paid detail assignments in different parts of the building -- part of a program where companies can hire NYPD officers in uniform to provide security. Some finance workers at an office building down the block were picking up dinner at a corner eatery when they heard a loud noise and saw people running. “It was like a crowd panic,” said Anna Smith, who joined the workers pouring back into the finance office building. They remained there for about two hours before being told they could leave. The building where the shooting happened is in a busy area of midtown, located a short walk north from Grand Central Terminal and about a block east of St. Patrick’s Cathedral. The city’s emergency management alert system warned of traffic delays, road closures and disruptions to public transportation in the area. Through late July, New York City is on pace to have its fewest murders and fewest people hurt by gunfire than any year in recent decades. This story has been updated to remove Deutsche Bank and J.P. Morgan from the list of offices at the Park Avenue building. Both no longer have offices there. Associated Press writer Mike Balsamo contributed from New York.