He uses matchbooks to ignite accelerants in crowded social hubs (like a cinema and a church) to maximize the "audience" for his destruction.

S4E19 - “House On Fire” - Unsubs: A Criminal Minds Podcast

The investigation focuses on the specific brand and type of matches found at the scenes in Royal, Indiana, as they are the arsonist's signature tool for ignition. Additionally, the episode highlights the lack of a for the unsub, which complicates the BAU's efforts to identify him through official records or history. Key Plot Details