President Donald Trump’s supporters faced off with protesters shouting “Black Lives Matter” Saturday in Tulsa as the president held his first campaign rally in months amid public health concerns about the coronavirus and fears that the event could lead to violence in the wake of killings of Black people by police.

Hundreds of marchers flooded the city’s downtown streets and blocked traffic at times, but police reported just one arrest as of Saturday afternoon. Many on foot chanted, and some occasionally got into shouting matches with Trump supporters, who outnumbered them and yelled, “all lives matter.” Later in the evening, a group of armed men began following the protesters. When the protesters blocked an intersection, a man wearing a Trump shirt got out of a truck and spattered them with pepper spray. Police later deployed an irritant gas to try and make the group disperse.

The Trump faithful gathered inside the 19,000-seat BOK Center for what was believed to be the largest indoor event in the country since restrictions to prevent the Covid-19 virus began in March. Many of the president’s supporters weren’t wearing masks, despite the recommendation of public health officials to keep the coronavirus from spreading. Some had been camped near the venue since early in the week.

Turnout at the rally was lower than the campaign predicted, with a large swath of standing room on the stadium floor and empty seats in the balconies. Trump had been scheduled to appear at a rally outside of the stadium within a perimeter of tall metal barriers, but that event was abruptly cancelled.

Trump campaign officials said protesters prevented the president’s supporters from entering the stadium. Three Associated Press journalists reporting in Tulsa for several hours leading up to the president’s speaking did not see protesters block entry to the area where the rally was held.

While Trump spoke onstage, protesters carried a paper machete representation of him with pig snout. Some in the multiracial group wore Black Lives Matter shirts, others sported rainbow-colored armbands, and many covered their mouths and noses with masks. At one point, several people stopped to dance to gospel singer Kirk Franklin’s song “Revolution.” The protesters blocked traffic in at least one intersection. Some Black leaders in Tulsa have said they’re worried the visit could lead to violence. It’s happening amid protests over racial injustice and policing across the U.S. and in a city that has a long history of racial tension. Officials said they expected some 100,000 people in Tulsa’s downtown.

The woman who was arrested was seen on live video sitting cross-legged on the ground in peaceful protest when officers pulled her away by the arms and later put her in handcuffs. She said her name was Sheila Buck and that she was from Tulsa.

Police said in a news release the officers tried for several minutes to talk Buck into leaving and that she was taken into custody for obstruction after police were asked by the Trump campaign to remove her from the area.

Buck was wearing a T-shirt that said “I Can’t Breathe” — the dying words of George Floyd, whose death has inspired a global push for racial justice. She she had a ticket to the Trump rally and was told she was being arrested for trespassing. She said she was not part of any organized group.

Several blocks away from the BOK Center was a festival-like atmosphere, with food vendors serving hot dogs and cold drinks and sidewalks lined with people selling various Trump regalia.

There was also an undercurrent of tension near the entrance to the secured area, where Trump supporters and opponents squared off. Several downtown businesses boarded up their windows as well to avoid any potential damage.

Kieran Mullen, 60, a college professor from Norman, Oklahoma, held a sign that read, “Black Lives Matter” and “Dump Trump.” “I just thought it was important for people to see there are Oklahomans that have a different point of view,” Mullen said of his state, which overwhelmingly supported Trump in 2016.

Brian Bernard, 54, a retired information technology worker from Baton Rouge, Louisiana, sported a Trump 2020 hat as he took a break from riding his bicycle around downtown Tulsa. Next to him was a woman selling Trump T-shirts and hats, flying a “Keep America Great Again” flag. Her shirt said, “Impeach this,” with an image of Trump extending his middle fingers.

“Since the media won’t do it, it’s up to us to show our support,” said Bernard, who drove nine hours to Tulsa for his second Trump rally.

Bernard said he wasn’t concerned about catching the coronavirus at the event and doesn’t believe it’s “anything worse than the flu.” Across the street, armed, uniformed highway patrol troopers milled about a staging area in a bank parking lot with dozens of uniformed National Guard troops.

Tulsa has seen cases of Covid-19 spike in the past week, and the local health department director asked that the rally be postponed. But Republican Gov. Kevin Stitt said it would be safe. The Oklahoma Supreme Court on Friday denied a request that everyone attending the indoor rally wear a mask, and few in the crowd outside Saturday were wearing them.

The Trump campaign said six staff members helping prepare for the event tested positive for COVID-19. They were following “quarantine procedures” and wouldn’t attend the rally, said Tim Murtaugh, the campaign’s communications director.