Using a pocketknife, Brown appeared to seek out certain colleagues at the facility in a Tallahassee industrial park.
Americans commemorated 9/11 with solemn ceremonies and vows Wednesday to "never forget" 18 years after the deadliest terror attack on American soil.
Mayor Paul TenHaken said the city was looking into a "breach of protocol" with its outdoor siren warning system.
"These guys were in the worst possible conditions you could imagine a human being to be in,"
The ceremony begins at 8:40 a.m. EST, at the 9/11 Memorial plaza at the World Trade Center site.
President Trump said U.S. peace talks with the Taliban are "dead."