BALTIMORE — A memorial park now sits on the site of the burning building on Stricker Street, which collapsed killing three firefighters almost four years ago, ultimately leading police to arrest 57-year-old James Barnett last week for allegedly setting the fire.

“This team processed every inch of the multi-building fire scene searching for the even smallest clue that caused the fire,” said ATF Asst. Special Agent in Charge Jon Earle.

WATCH: Families' grievances remain over firefighters' deaths Families' grievances remain over firefighters' deaths

Investigators say they conducted hundreds of interviews, screened hundreds of hours of video and performed more than a thousand scientific tests to make sure they got it right, and through their attorney, the victims’ families acknowledged t

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