BROCKTON — A Middleborough man and his stepson were arrested near the site of a blaze in West Bridgewater Wednesday night and charged with arson, an arrest authorities believe will solve a string of mysterious fires across the region that have dogged them for months.
The arrests came after police secretly planted a GPS device on vehicles owned by one of the defendants.
“A serial arsonist strikes fear in the public and creates a great deal of anxiety,” state Fire Marshal Stephen Coan said in a press conference Thursday about two hours after Mark Sargent, 45, and Jeanmarie Louis, 23, were each charged in Brockton District Court with burning a building and attempting to burn a building.
Attorneys for both men pleaded not guilty on their clients’ behalf. Sargent and Louis were ordered held pending a dangerousness hearing Feb. 6.
Authorities said that Sargent is a suspect in 24 arsons and that they are looking at Louis’s possible involvement in the fires.
The scores of vacant and abandoned buildings set ablaze since September stretched across four counties south of Boston and included houses, a barn, a restaurant, and a boat. The structure ignited Wednesday night, an unfinished commercial building at 457 Rear South Main St., West Bridgewater, was minimally damaged, unlike many of the others.
Coan and Plymouth District Attorney Timothy J. Cruz declined to discuss a possible motive for the fires. While no one lived in the burned structures, at least six firefighters suffered minor injuries while battling the blazes.
In November, as the number of cases approached 20 and investigators saw patterns pointing to a serial arsonist, Coan called a summit at Bridgewater State University, bringing together fire chiefs and law enforcement officials from Barnstable, Plymouth, Norfolk, and Bristol counties.
A break in the case came a week before Christmas. When fires broke out shortly after midnight Dec. 20 in three boats at the Marshfield Marina, police searching the area found Sargent, “very nervous,” sitting in his Toyota Highlander nearby.
When “they asked him why he was there at that location, he said he was driving around, that he does it all the time,” said Tim Kenny, an assistant Plymouth district attorney, said during the arraignment. “He said he had no friends in the area. . . . He saw that fire and decided to sit there and watch it.”
Within two days, police obtained a warrant and attached a GPS device to the Highlander.
In interviews, Sargent told police that he had a stepson, Louis, and they already had information linking him to one arson: He was seen in the area of a suspicious fire on Monponsett Street in Halifax on Nov. 26 and used his credit card to make a purchase at a nearby Cumberland Farms, Kenny said.
Kenny said the GPS tracking device showed the Highlander had passed by seven arson locations at the times the fires were set, including 304 Turnpike St. in Easton, 775 Washington St. in Hanover, and 1958 Broadway in Raynham.
In early January, Sargent traded his Highlander for a silver Subaru Outback, and authorities soon had a GPS tracking device placed on it.
At 8:29 p.m. Wednesday, the Outback was driven past the site of the fire in West Bridgewater several times, Kenny said. At 9:15, it stopped for about 10 minutes about a mile and a half from the scene.
At 9:35 p.m., the fire started, and five minutes later, the Outback passed the scene. Moments later, police stopped the vehicle, Kenny said.
Sargent was sitting in the driver’s seat and Louis was in the front passenger’s seat, his pants and shoes wet with mud. A strong smell of gasoline emanated from inside the vehicle and police found a pair of gloves in Louis’s pockets, Kenny said during the arraignment.
Both men were arrested.
Coan commended his team of investigators, saying they worked tirelessly, including through the holidays on the case.
“The fires have occurred over a large footprint, and that has added to the complexity of the investigation,” he said during the press conference.
Kenny said the list of suspicious fires that authorities need to investigate is lengthy.
“There have been 38 fires, incendiary fires, south of Boston since September of 2012 and in investigation, 24 of those fires have been found to be linked to the same suspect or suspects based on modus operandi,” Kenny said.
Authorities are continuing their investigation to determine whether Sargent and Louis played a role in the 14 other cases.
Cruz said authorities had no timetable for when they might bring additional charges against the men.
Sargent’s former wife, Marie Cingolani of Avon, said in a brief phone interview that they had a turbulent marriage, which ended several years ago.
“I’m literally sick to my stomach” over the arsons, she said.
Sargent’s occupation according to the police report, is “auto wholesaler,” and he is self employed; Louis, who also lives in Middleborough, is unemployed.
Public records showed that Sargent declared bankruptcy in 1995. In recent years, he had worked at two car lots in Brockton, records indicate.
Toni Iafrate, the owner of the building that was set afire in West Bridgewater, said one of her tenants at a nearby property saw a shadowy figure wearing a hoodie emerge from the structure and run away before the fire erupted.
The building, to be named Red Varn Acres, was swathed in thick fire-retardant material that probably prevented extensive damage, she said.
“Nice to know that stuff works,” she said.Peter Schworm of the Globe staff contributed to this report. Brian Ballou can be reached at email@example.com. Follow him on Twitter@GlobeBallou.