By Alecia Reid

PHILADELPHIA (CBS) — Investigators said Thursday the massive fire at St. Leo The Great Church in Tacony was intentionally set. Now, authorities are offering a $20,000 reward for information leading to the arsonist.

St. Leo’s was a staple in this community for decades. Even after it went vacant, families held on to those memories. Now, investigators say someone intentionally set the building ablaze.

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The historic building is now a shell of what it once was.

“I can’t believe somebody would do this,” Tacony resident Charlene Riedel Choate said.

The walls are standing, but everything inside is charred debris.

Certified ATF investigators, who are trained in fire signs, were able to gain access and ruled this fire an arson.

“ATF always responds to church fires. This is one of our primary missions, at least in the A&E function, which is the arson and explosive function,” ATF Supervisory Special Agent Charles Doerrer said.

Due to extensive damage, firefighters had to knock down the church’s steeple, in fear it would eventually topple over.

For generations, Choate’s family celebrated milestones at St. Leo’s.

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“We all went to church here, to school here. We did all our sacraments, we buried our family members here. It was everything, it was our life,” she said.

Now emotional, she’s taking in what’s left of it. The building was vacant for years and was purchased about a month ago. Investigators say the new owner is cooperating with authorities and is not a suspect.

“As I understand it, he either tries to rent it to another congregation and a lot of times he gets dance studios or performing arts people that are interested in running it and one of those plans is what he was hoping to do with this place,” Doerrer said.

ATF, Philadelphia Police and the Fire Marshal’s Office are working together to investigate this crime of violence.

There is a $20,000 reward for information leading to the arrest and conviction of the person or people responsible for setting the fire.

Officials say you may have seen something that you think is insignificant but could be critical to the case.

Anyone with information on the person or persons responsible for the fire should contact ATF at 1-888-ATF-TIPS (888-283-8477), email ATFTips@atf.gov, or contact ATF through its website at www.atf.gov/contact/atftips. Tips can also be made to the Philadelphia Fire Marshal’s office via mobile device by following: bit.ly/PHLarsontips.

Tips may also be submitted to ATF using the ReportIt® app, available on both Google Play and the Apple App Store, or by visiting www.reportit.com.

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All calls and tips will be kept confidential.