What began as a peaceful gathering of people hoping to see President Barack Obama Thursday night… What began as a peaceful gathering of people hoping to see President Barack Obama Thursday night became an eight-hour-long protest-turned-riot that damaged Oakland businesses and prompted police to use force.

About 50 people gathered near the bridge closest to Schenley Plaza at 4 p.m. Thursday to see Obama’s motorcade drive to the Phipps Conservatory.

Obama and his wife, Michelle, hosted a working dinner in the greenhouse for the other G-20 leaders and their spouses. It was a precursor to the G-20 Summit, which officially opened Friday morning.

The gathering was peaceful until protesters joined the original group around 6 p.m.

As the crowd grew, police sent in reinforcements and placed caution tape near the traffic light at the bridge.

Demonstrators ripped the tape and began leapfrogging over one another and toward the police.

Police declared the event an “unlawful assembly” around 6:30 p.m. and warned protesters, in both English and Spanish, that if they didn’t leave, they could be arrested or “subject to other police action.”

When the people didn’t move, police launched a smoke bomb into the group.

It was the first of many times police would fire gas or smoke into the crowds, which eventually grew to include hundreds of, if not more than 1,000, people.

The crowd simmered down for a few hours after the initial smoke bomb, at one point dancing to music provided by the Pittsburgh Hare Krishnas.

“It’s impossible for us to be stronger than them,” one man said about the police. “They’ve got sticks and shields, but we’ve got voices and we can all sing and be louder than them.” The man claimed to be a chaitanya, or leader, of the Hare Krishnas.

Other groups began protesting around 10 p.m.

People dressed in all black and wearing bandanas marched throughout Oakland screaming, “We’re here. We’re queer. We have no fear.”

Many other people, most of whom looked college-aged, joined the march.

Some of the protesters broke the storefront windows of McDonald’s, FedEx Kinko’s, The Pitt Shop, Pamela’s Diner and Bruegger’s Bagels, among other businesses. They also lit Dumpsters on fire.

The group eventually joined the people protesting in Schenley Plaza and around the Cathedral of Learning.

They showed up just in time to hear the police once again declare the event “an unlawful assembly” at 10:37 p.m. over a loudspeaker system.

Police threw more than 30 canisters of gas into the crowds, which were made mostly of college-aged people, throughout the night.

Police surrounded the Cathedral around 11:30 p.m. and eventually covered the lawn of the William Pitt Union.

At one point, they marched through the Schenley Quadrangle and onto the Litchfield Towers patio.

Popping sounds could be heard from the Union.

After one round of the sounds, one man laid on the Pitt logo that’s on the ground of the William Pitt Union patio near Forbes Avenue.

Officers with batons hovered over the man, who took several minutes to stand up.

Police eventually handcuffed him.

The police had said they would use “less lethal weapons” on people who wouldn’t disperse.

Videos on YouTube show students getting trapped in the stairwell above the Pitt police substation on Forbes Avenue.

Police at one end of the stairwell were telling them to move up the steps, but officers at the top of the stairs were telling them to move down the steps.

One ACLU volunteer said he was disappointed in the way the police handled the protests.

“They are just kids,” Dave Ninehouser, an ACLU legal observer, said. “They need to call their parents and cry bloody murder.”