The speed and deadliness of recent high-profile shootings have prompted police departments to recommend fleeing, hiding or fighting in the event of a mass attack, instead of remaining passive and waiting for help.

The shift represents a “sea change,” said Chuck Wexler, executive director of the Police Executive Research Forum, which recently held a meeting in Washington to discuss shootings like those in Newtown, Conn., and Aurora, Colo.

The traditional advice to the public has been “don’t get involved, call 911,” Wexler said, adding, “There’s a recognition in these ‘active shooter’ situations that there may be a need for citizens to act in a way that perhaps they haven’t been trained for or equipped to deal with.”

Wexler and others noted that the change echoes a transformation in police procedures that began after the shooting at Columbine High School in 1999, when some departments began telling officers who arrived first on a scene to act immediately rather than waiting for backup. Since then, the approach has become widespread, as a succession of high-profile shootings across the country has made it clear that no city or town is immune and that police agencies must take an active approach.

“We used to sit outside and set up a perimeter and wait for the SWAT team to get there,” said Michael Dirden, an executive assistant chief of the Houston Police Department. “Now it’s a recognition that time is of the essence and those initial responders have to go in,” he said, adding that since the Virginia Tech University shooting in 2007, the department has been training first responders to move in on their own when they encounter active gunfire.

Research on mass shootings over the past decade has bolstered the idea that people at the scene of an attack have a better chance of survival if they take an active stance rather than waiting to be rescued by the police, who in many cases cannot get there fast enough to prevent the loss of life.

In an analysis of 84 such shooting cases in the United States from 2000 to 2010, for example, researchers at Texas State University found that the average time it took for the police to respond was three minutes.

“But you see that about half the attacks are over before the police get there, even when they arrive quickly,” said J. Pete Blair, director for research of the university’s Advanced Law Enforcement Rapid Response Training Center and an author of the research, which is set to be published in a book this year.

Two instructional videos, one produced by Houston’s Office of Public Safety and Homeland Security and the other by the University of Wisconsin’s police department, recommend that civilians fight an attacker if options such as escaping or hiding are not available.