WASHINGTON — Is your workplace getting shot up by a crazed gunman?

No problem — just grab a pair of scissors and fight back!

That’s some of the helpful advice in a new instructional video from the Department of Homeland Security that was posted on the agency’s Web site just a month after the massacre at Sandy Hook Elementary School in Connecticut.

“If you are caught out in the open and cannot conceal yourself or take cover, you might consider trying to overpower the shooter with whatever means are available,” says the narrator in the video, which shows an office worker pulling scissors out of a desk drawer.

The video, titled “Options for Consideration,” also advises that people who get caught in an “active shooter” situation should run away, hide under a desk or take cover out of the line of fire.

The nearly four-minute-long video opens with chilling scenes from the 2007 Virginia Tech massacre, the 2009 mass shooting at Fort Hood in Texas, and the 2011 attempted assassination of Gabrielle Giffords.

But the video quickly shifts to hokey footage of office workers scampering under desks, crouching in corners and racing into closets to hide from a rampaging gunman on the loose.

“To protect your hiding place, lock the door if you can. Block the door with heavy furniture,” recommends the male narrator, speaking in measured, authoritative tones.

Other survival strategies promoted in the video include hiding “behind large items such as cabinets or desks. Remain quiet. Silence your cellphone or pager. Even the vibration setting can give away a hiding position.”

Richard Feldman, president of the Independent Firearm Owners Association, said he has a better option for consideration than a pair of scissors when confronting an armed mass murderer — a legal firearm.

“That’s why I prefer a gun, and I usually do carry a gun when it is lawful to do so,” said Feldman. “Clearly, you use whatever you can” to fight for your life, he said.

So if scissors are all you’ve got, grab them by all means.

The video is part of the Obama administration’s ongoing campaign to reduce firearm violence in the wake of the horrific mass murder last month of 20 children and six teachers in Newtown, Conn., said a Homeland Security official.

Homeland Security has operated an active-shooter preparedness-training program for years, and the “Options for Consideration” video was in production prior to the Dec. 14 shooting in Newtown.

The video was released to coincide with President Obama’s sweeping proposals to curb gun violence in America, said the official.

Obama’s most controversial proposals include a ban on military-style assault rifles and high-capacity ammo clips, as well as expanded background checks for firearm purchases.

Security consultant Andrew Scott called the information in the video “adequate.”

He conceded that Homeland Security was correct in recommending that people use scissors to attack a gunman but only in a “last, worst-case scenario.”

“Just the suggestion [to fight back] is a positive move,” said Scott, a former SWAT commander in North Miami Beach. “You don’t want to be sheep for the slaughter.”

But if you do arm yourself with shears, the narrator warns you to drop them when cops arrive.

“Put down any items. Immediately raise your hands,” is the closing advice.