The officers sat in the cool of the Phoenix Municipal Court basement watching DVDs on laptop computers, reading books and dozing off with their riot helmets as pillows, waiting patiently for the protesters to arrive.
As the crowd swelled near Phoenix City Hall, the officers moved in formation to clear the street of protesters and journalists amid chants denouncing Senate Bill 1070.
Phoenix deployed several hundred police along Washington Street and other busy downtown streets on Thursday, led by a core group of about 150 crowd-control officers carrying detailed protest plans.
By midday, more than 20 protesters were in custody, including women and youngsters who linked arms in solidarity before they were led off the street.
A mile away from the action, operation chiefs were calling shots from the second-floor of a Phoenix Fire Department administration building as part of a coordinated effort spanning multiple law-enforcement agencies. Police leaders said they aim to overstaff security for large-scale protests and other major events to ensure backup for officers on the front lines.
Thursday morning's march and protests were mostly peaceful, though tactically trained officers know that any major event can turn violent quickly.
"It can go from peaceful to riotous in a second," Phoenix police Sgt. Ed DeCastro said. "It just takes one sentence or a bottle being thrown."
Phoenix trained additional precinct patrol officers in crowd-control tactics after April's protests in downtown and near the Capitol, in which high-school students funneled unexpectedly into the area en mass.
Phoenix police Lt. Jeff Lazell, who oversees tactical-response teams through the Phoenix Police Downtown Operations Unit, said the goal was to prepare officers citywide in case of any unexpected violence that would force them into critical supporting roles downtown. Training included tactics on forming "skirmish-lines" to safety disperse unruly crowds.
"We trained about 1,200 officers in 10 days," Lazell said. "To coordinate that kind of training is an undertaking."
Command-center operations began at 6 a.m. Staff wore headsets tuned to a secure radio frequency for event communications and kept watch over video screens showing live feed from SB 1070 hot spots: the federal courthouse, Wells Fargo building, Cesar Chavez Plaza, Maricopa County Fourth Avenue Jail, and a building housing Immigration and Customs Enforcement.
Lt. Brian Lee, operations chief, said street activity was fairly quiet for much of the morning; most police activity was limited to assisting a group of 150 to 200 demonstrators safely wind their way through the streets.
"As far as expectations, it's really kind of hard to tell with this group," Lee said. "We have people coming in from out of state; we have other people that aren't part of our local community. We try to get as much information as we can on what their intentions are, but a lot of it is reactionary because we just don't know what they plan to do."
Radio traffic started to pick up about 9 a.m., as demonstrators began to swarm around First Avenue and Washington Street. Images of the group flashed from flat-screen TVs hanging overhead in the four corners of the room, each tuned to local and national news stations.
At 9:06 a.m., a voice crackled over the command radio channel.
"We've got 150 or so people at Washington," the voice said above a din of crowd activity. "Game plan is they're supposed to come over at 10 or 10:30. We'll have some issues at that time."
Command-center staff gathered around the live feed as, like clockwork, people began to flood Washington Street at 10 a.m., blocking in westbound vehicles.
At 10:15 a.m., another voice came over the command channel: "Be advised, we have initiated our first warnings" for pedestrians to get out of the street. "We're going to issue second warnings. In 10, we'll start issuing number ones," or arrests.
Twelve minutes later, another voice: "OK, we're going to go ahead, start making our first arrests. Arrest the gentleman in the gray hat."
Within seconds, live TV feed showed four officers closing in to cuff the man and lead him away to a white van. One by one, the command was issued to arrest four people who had been standing in a line next to the man in the gray hat.
And one by one, they were led away.