Metro

No. 1 with a bullet

When a gun-wielding maniac starts shooting up the workplace, duck behind a file cabinet!

That’s the safest place for workers who can’t escape the room or building entirely, the NYPD says in a new study it hopes will save lives.

“During an actual event, the NYPD recommends avoiding the shooter and evacuating immediately,” said Capt. Michael Riggio of the department’s Counterterrorism Bureau.

Hiding behind a file cabinet is probably the best “Plan B” — and the Police Department proved it by shooting up different kinds of office furniture.

Cubicle partitions provided no protection from bullets or shotgun pellets, and desks were little better. But file cabinets stopped bullets from a .38-caliber Smith & Wesson, a 9mm Glock and a shotgun. Only bullets from an AK-47 passed through.

The recommendations, prepared for building security personnel, are from a Counterterrorism Bureau study of more than 200 “active shooter” incidents over the last 44 years.

The study was prompted by the 2008 terror attacks in Mumbai, said Police Commissioner Ray Kelly.

“Unfortunately, there are no off-the-top-shelf easy templates to apply to these situations,” Kelly said.

Riggio had plenty of other advice on how to react to a school or workplace gunman.

“If an evacuation is not possible, barricade and hide in a predetermined safe room, or any room that is available,” he said.

If the room has windows, try to cover them. “We don’t want the shooter to possibly see you inside,” Riggio said.

“Hide behind as many layers of cover as possible. Silence your cellphone and remain silent,” he said.

As a last resort, cops say, try to take the gunman down.

“If no other option is available, and you are confronted with the gunman, we recommend trying to confront him with physical force as quickly and as aggressively as possible,” Riggio said.

“Consider using pens, staples, chair legs, anything you can get your hands on, as an improvised weapon.”

If you’ve got to take down the gunman, it’s best to act as a group, he added.

Most active shooters are members of the communities they target — such as relatives, co-workers or fellow students, say cops. About a third of active shooter attacks occur at schools, and about half occur in workplaces, such as office buildings, factories and warehouses.

lorena.mongelli@nypost.com