On Saturday, “an individual committed arson on a newly purchased ICE building” by breaking a window, igniting a fire and throwing a propane tank into the building, according to a U.S. Department of Homeland Security spokesperson.
“The fire was quickly extinguished by the interior sprinkler system,” DHS said, noting that the suspect fled the scene after setting the fire. “The matter remains under investigation by the FBI.”



You’d want a flammable liquid so that it floats on the water and spreads more the wetter it is.
Here’s some reading on why https://www.nfpa.org/news-blogs-and-articles/blogs/2024/08/12/what-is-a-class-k-fire-extinguisher
Good luck with your story.