Sacramento Bee -- A test of the emergency broadcast system for the upcoming Democratic National Convention in Los Angeles was held in Grass Valley last week.Sgt. Jeff Swatman - his real name - of the Stockton Police Department led members of his force in and out of local vacant businesses in Special Weapons and Tactics, or SWAT team exercises.Blasts from officers' weapons could be heard blocks away at an environmental protest in Memorial Park. Members of the Stockton and Alameda police departments stormed into the old Spruce Cleaners behind the old U-Save liquor store on Colfax Avenue. Lime-green swastikas and obscenities were spray-painted on the wall over a tidy blue-lettered list of the cleaner's former services. Bags of lost clothes were strewn around one corner of the dry cleaners.For the 16th year, the Grass Valley Police Department organized the SWAT team school so teams could practice several "scenarios" each day in area locations.Albert Buchter, a Nevada Union High School sophomore and a member of Grass Valley Police Department's Sgt. Jerod Johnson's Boy Scout Troop, was recruited to be one of the troublemakers giving the SWAT team a hard time."Keep your hands where we can see them. Walk straight back," an officer instructed one of the youths recruited to participate in the officer rescue exercises.Fellow Scouts Josh Newton, Heath Randall and Cole Wheeler joined Buchter. Will Porter, a Sierra Mountain High School student, also volunteered to get in the way of paintball guns."Are you able to move?" an officer yelled to a hidden menace. "Is there anyone else in the room? Are you injured? Or do you have any demands?"A Stockton police officer navigated a mirror at the end of a long pole to see if a suspect was hiding around a corner in the old commercial building.Several law enforcement agencies used the same telecommunications system during the drills to test the system. A failure to communicate can be a big problem in emergencies.The state Office of Emergency Services provided radio communications for the teams participating in last week's training.Johnson said earlier that one of the biggest problems police have is agencies operating on different radio frequencies. SWAT teams are known by different names in different agencies. The Oakland Police Department calls its team the "tactical operations team." The Grass Valley Police Department has its "special incident team."The Grass Valley SWAT team school is certified by Police Officers Standards and Training, a state board.Although the teams return to Grass Valley each year for the training, the sight of officers in black spilling out of a white van and running into a boarded-up building or local high school can catch residents by surprise.This was only a test.