REVERE – The idea of watching a SWAT team storming your neighbor’s house may seem far off to many.But in an age where domestic violence horror stories are in the news far too often and the words “school shooting” have become a common phrase, Revere police realize a life-threatening situation will have to be diffused when they least expect it.On a recent Wednesday when Revere High School students were on April vacation, 12 members of the Revere police department’s Special Operations Unit spent eight hours training for the worst.”It’s the sort of thing you don’t have the luxury of time waiting for,” said 44-year-old Lt. Joseph Cafarelli.On this day officers showed how they would use a “flash-bang” device, which is thrown into a room where the perpetrator of a standoff is located. The device gives a quick but small explosion that is just loud and smoky enough to distract the suspect and give SWAT members enough time to move in.”It buys three to five seconds,” Cafarelli said. “It can be a lifetime.”Like most Special Weapons And Tactics teams in medium- to large-size police departments, Revere’s SWAT team is meant to diffuse high-risk scenarios that are deemed too dangerous for patrolmen, but could be handled without calling in the larger-scale, State Police SWAT team.”It’s anything that a police officer with normal training and equipment can’t handle,” 54-year-old Lt. Carl Ruggerio said.The Special Operations Unit has been used for approximately 12 high-risk situations in the past five years, police said. One example occurred on June 28, 2007, when SWAT members secured an apartment at 12 Jones Road and recovered a stolen high-capacity firearm that was used in an earlier assault. The suspect, Angel Perez, 26, of Malden, was recently sentenced to two years and six months in prison.High-risk scenarios include carrying out warrants for violent suspects, barricade situations, active shooter situations, armed and dangerous individuals, high-risk apprehensions, high-risk vehicle stops and assisting an emotionally disturbed person. The lieutenants say police training has been enhanced in recent years.”A lot of things have changed since Columbine,” Cafarelli said. “Every officer is trained in active shooter response.”The officers on this day chose to use RHS as a training ground, somewhat out of convenience because students had the week off, but also to prepare for an active shooter inside a school – a scenario everyone hopes will never happen.For several hours, the officers coached each other on how to carefully maneuver around sharp corners and point rifles down long hallways.The Special Operations Unit also trained outside on a school bus in the event that a robber or a hostage taker would hold victims on a bus.The officers explained that several larger communities, including Revere and Lynn, have their own SWAT teams operating within their own police departments. Smaller communities such as Saugus and Peabody participate in the North Eastern Massachusetts Law Enforcement Council, a SWAT team that serves several communities that are located close to each other.Even on their days off, Revere SWAT members are on-call 24/7.”That’s happened more than once. You’ll get a phone call at 2 a.m. and you’re called out of bed,” said Ruggerio, adding that unless a SWAT member is on vacation a long distance away, they must respond for duty anytime, day or night.The Los Angeles police department’s SWAT team was one of the first created in the United States. Several retired officers now teach SWAT trainees all across the country.”They were the first ones to do it in the 1960s,” Ruggerio said. “There’s no textbook. We learn from their mistakes, and they tell us that.”In order for officers to join Revere’s Special Operations Unit, they must have firearms expertise and pass a rigorous fitness test, which consists of a one-mile run in under 12 minutes, a 60-yard dash while holding a 45-pound ramming device and wearing a gas mask, a 30-yard crawl with the m