Officials said five adults and one juvenile have been charged in connection with nine arsons in Jeannette from 2008 to 2012.
Agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives said it's unusual to have more than one serial arsonists at one time, but in this case, they have found six.
The ATF has been investigating since February, when an apartment building fire left nine people homeless. At the time, Jeannette fire officials said it was the city's 12th arson or suspicious fire since October.
"People can rest easy now," said Westmoreland County District Attorney John Peck, who announced the arrests during a press conference Wednesday morning. "People behind these numerous fires are under arrest."
Police said the six people charged live in the same area, but they didn't explain how the suspects know each other or how they worked together.
Don Robinson, assistant special agent in charge of the Philadelphia ATF office, said his office got involved with the investigation in February.
"It's kind of unusual in a serial arson case to have more than one actor," he said. "Usually, it's just one person."
"When you get to serial arson, there can be more than one fire-setter at a time, but it's highly unusual that we see six or more working together to set that many fires," ATF officer James Tanda said.
Channel 11's Courtney Brennan obtained a criminal complaint naming brothers Roger Adair, 26, and Richard Adair Jr., 27. Police charged them with two counts of arson, criminal trespassing and risking a catastrophe.
Brennan reported that the Adair brothers are charged with setting a fire on Nov. 18, 2010, at 118 N. 5th St.
Richard Adair Jr. is also charged with setting fires on Aug. 24, 2010, at 212 N. 5th St., and on Oct. 19, 2011, on South 6th Street.
Police said John Horne, 21, Jeffrey Tierney Jr., 23, and Christopher Jones, 22, also face similar charges in connection with other arsons in the area.
"It's done," Jeannette Police Chief Brad Shepler said. "Our city can rest a little bit easier. I can rest a bit easier now."
Peggy Wagner said she was one of the many Jeannette residents who was afraid to go to sleep and panicked every time she heard a siren go off.
Wagner cheered from the sidewalk Wednesday as Tierney was arrested.
"I was in my living room watching TV, and I heard, 'Get down on the ground right now!'" Wagner said. "They had him out of the car and already handcuffed."
Firefighters like James Swartz said it felt like he was fighting two or three fires per day, including one on Chestnut Street in February.
"I bent down, put my mask on and 'bang!' I heard a bang, and the next thing I know I was on the ground, hit by glass," Swartz said.
Authorities said the glass sliced through Swartz's neck, and because of that, two of the suspects are facing an extra charge of aggravated assault.
"The nurse in the emergency room at Presby said I had a guardian angel, and I told her I thought I had a couple up there," Swartz said.
Investigators have not commented on the suspects' motivation behind the fires.