MADISON, Wis. -- A prominent south Madison community activist and his longtime partner were killed in a fiery plane crash in Joliet, Ill., Thursday night.

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The National Transportation Safety Board said it appears a small, two-seater plane carrying the couple was taking off at Joliet Regional Airport when it "took a hard left," flipped over and crashed into a field just before 9 p.m. Thursday.

NTSB officials said Friday that the cause of Thursday night's crash was still unclear, but it appears the couple had stopped to refuel.

The Will County coroner's office tentatively identified the victims as Stuart Seffern, 50, and Deborah Loiselle, 52, both of Madison. The coroner's office says autopsies are planned Saturday.

Joshua Stabenau, the manager of Madison Area Carpet Cleaners, told WISC-TV that the Dane County Sheriff's Department called him to advise that Seffern and Loiselle were killed in a crash Thursday night.

NTSB officials said the plane appeared to be flying from Orlando, Fla.

A Federal Aviation Administration spokeswoman says the plane was a Lancair 360 single-engine plane. Such planes are typically purchased as kits and home-built.

"We'll look at wreckage, what's left of it, (and at) flight control continuity, (to determine) if the aircraft was operating the way it should've been," said Pam Sullivan, a NTSB safety investigator.

Stabenau said Seffern was "tied into everything" in the community and knew many people. He was a member of the homebuilt aircraft flying club Lantzair Flyers, Inc., and on the board of directors of the Mendota Yacht Club.

He was also active in the Burr Oaks Neighborhood and South Madison issues. He was vice-chair for the South Madison Planning Council and a Congressional District representative of the Libertarian Party of Wisconsin, Stabenau said.

Loiselle worked at the state Capitol.

The couple lived in one of Madison's most challenged neighborhoods, and they're being remembered for their community service. In particular, everyone from the mayor to neighbors is honoring the outspoken activism of Seffern.

Those who knew him said Seffern wasn't afraid to speak out for -- or against -- any civic issue he saw as important.

On Friday, Madison Mayor Dave Cieslewicz said in that statement that he didn't always agree but noted that Seffern "was a tireless advocate for his south side community."

"He committed a tremendous amount of time and energy to the betterment of his neighborhood, and his strong voice will be missed," Cieslewicz said in the statement.

Those who worked closely with Seffern and Loiselle, his companion for more than 30 years, said it's hard to believe they've lost their friends and two longtime community activists.

"It's quite a shock, losing both of them at the same time," said Dale Cox, president of the Burr Oaks Neighborhood Association.

Neighbors said they were both completely dedicated to their Burr Oaks neighborhood.

"They had been together a long time, and I don't think it's going to fee real until after a few meetings and Stu and Debbie aren't at the meetings," said Ruth Ann Bauhs, of the Burr Oaks Neighborhood Association.

Neighborhood association officials said Loiselle would even dress up like the Easter bunny for the local Easter egg hunt. Both would throw neighborhood parties, and Seffern was known for passionately speaking out about issues that affected his challenged neighborhood or the south side in general.

"You never knew what was going to come out (when he spoke). He was bigger than life, and he was just a good person," said Sheri Carter, head of South Madison Metropolitan Planning Council.

Carter worked with Seffern on the South Madison Metropolitan Planning Council for four years. She called him a champion for south Madison.

Friends and neighbors are also remembering Seffern for starting the nightly neighborhood walks to fight crime.

When he crashed, Seffern was flying the Lancair 360 he apparently helped build and recently bought. The couple had been in Buffalo, N.Y., then flew to Florida and was on their way back.