Pointers include yelling at or subduing the shooter in some situations, but mostly, the advice is to evacuate or hide, Bloomberg reports. With so little time for police to react, says Paul Browne, spokesman for the New York Police Department, it’s up to the intended victims to try to avoid the carnage until help arrives.

A 2011 report from the NYPD found that 281 mass shootings occurred between 1966 and 2010, and many of the most lethal incidents happened in the last decade, the article notes.

Since the “Active Shooter Program” began four years ago, 125,000 people in the government and private sector have been trained in the seminars, online course, booklets and other guides it offers, according to Peter Boogaard, a spokesman for the Department of Homeland Security, in the article.

Joseph LaRocca, senior adviser a the National Retail Association, a Washington-based trade group, said he approached the DHS about doing the booklet after a gunman killed eight and then took his own life at the Westroads Mall in Omaha, Nebraska, in December 2007, Bloomberg reports. The booklet was released in October 2008.

The article says that while the safety of retail employees and customers was the main reason, LaRocca said that his members were also concerned about the legal liability they would face for not trying to do anything to minimize the loss of life during an active shooter incident.

Other advice offered by the booklet includes:

• Keep your hands visible with spread-out fingers so police arriving on the scene don’t mistake you for the shooter.
• If escape is impossible, silence cell phones and barricade the door of a safe room with furniture.
• Avoid “pointing, screaming and/or yelling” at police.
• Don't ask police or rescue forces for evacuation directions – proceed in the direction from which officers are entering the premises.
• If the possibility of death is imminent, shout at the attacker or throw items and improvise weapons to subdue the shooter.

Some cases have shown that simply yelling at a shooter has disrupted the “loop” of homicidal thinking, slowing the attack, the article says.

The best advice in the department’s materials are the tips on recognizing potential shooters, says Robert Siciliano, a Boston-based security consultant. DHS recommends that supervisors and officers look out for people  who are suicidal or make comments about “putting things in order,” talk of financial problems or have “empathy with individuals committing violence.”