Thousands marched in downtown Chicago protesting war, heading toward a convention center where President Barack Obama hosted a NATO summit.
Police dressed in riot gear stopped them and asked the crowd to disperse. The majority of the protesters left; some did not.
Then violence broke out.
A group of Tampa law enforcement officers witnessed the whole thing. They attended the summit last weekend to compare how their security plans for the Republican National Convention compared with the Windy City's strategy for the summit.
The clash between police and protesters was eye-opening, said Hillsborough County sheriff's spokesman Larry McKinnon, who attended the summit.
The confrontation started when a group of what he called "anarchists" began taunting police.
"They were prepared to engage in conflict," McKinnon said. "They were wearing gas masks and they had their own medics. They had their own videographers."
McKinnon said officers asked the crowd to disperse at the end of the march. Those who stayed started provoking police, who were dressed in riot gear. When the stragglers wouldn't leave, officers tried to remove them by force.
Some protesters hurled sticks and bottles at officers, who responded with batons. Four officers were injured, including one who was stabbed in the leg, and 45 people were arrested.
Protesters in Chicago were prepared for a confrontation, but Tampa officers said that when the GOP convention comes to town, they'll be ready, too.
"We have the resources in place," McKinnon said. "Hopefully, we won't use them."
Chicago police were praised for the restraint they showed during the summit. Protesters were given wide latitude and space to voice their political opinions, and police kept an eye out for criminal activity at major intersections and mingled with the crowd, said Tampa Assistant Police Chief John Bennett, who also attended the summit.
Even when things got testy and some protesters tried to provoke police by yelling in their faces, officers remained stoic and held their ground.
That's the kind of patience local officers are aiming for, Bennett said. After witnessing the events surrounding the summit, Bennett said he came to the conclusion that Tampa's convention security plans are on a similar track to what Chicago had in place.
"Our planning strategies were in sync," Bennett said. "We tried to find as many comparable events that we could."
Bennett said there was no "a-ha moment" where he felt Chicago police thought of something Tampa's officers didn't when it came to security for big events. In fact, plans for both cities were drawn up along identical lines.
Bennett declined to discuss the specifics of Tampa's security plans for the Aug. 27-30 convention. But he did mention broad examples of how officers are being trained to handle the thousands of people expected to protest downtown.
"Chicago is not Tampa and NATO is not the RNC. But we saw patience from police officers and a wide berth for First Amendment rights," Bennett said. "We'll also have that wide berth."
Some protesters in Chicago tried to provoke officers who were "just monitoring the crowd" by "yelling and screaming in their faces," he said. But police kept their cool and showed patience. Officers working the convention in Tampa "are being trained the same way," Bennett said.
McKinnon said Tampa law enforcement is hoping for a GOP convention with peaceful protests, but the city also is preparing for potential terrorism threats and violence.
But what happened on the summit's last day shows that some people aim to incite violence, McKinnon said.
Jared Hamil has a different account of the clash between protesters and Chicago police. Hamil, an activist with a group that will protest at the GOP convention in August, said he was in the crowd of protesters at the NATO summit.
"There was no violence whatsoever until police showed up at the very end and tried to get people to leave," Hamil said. "They showed up in riot gear. They showed up ready for war. Police showed up and started pushing people."
Chicago police also arrested three men on terrorism conspiracy charges, stemming from an allegation they tried to make Molotov cocktails ahead of the summit.
McKinnon said it would be "naïve to think that type of activity won't happen here. When you see it, it's shocking and ugly and it's something law enforcement doesn't want to be involved in."
Bennett said the police presence at the convention will be similar to officers patrolling Gasparilla. They will monitor the crowd and intersections and will "respond appropriately to criminal activity."
The U.S. Secret Service is the lead agency for security at the convention, which is designated a national special security event. Tampa has received $50 million from Congress for convention security. About $14 million has been spent on surveillance cameras, vehicles, bicycles, radios, protective gear and other equipment.
The federal grant also will pay for hotel rooms for at least 3,000 visiting police officers who will work during the convention.