Kirby police and firefighters are investigating a series of suspicious brush fires. Police responded on Thursday morning to a reported grass fire at Hugo Lentz Park. Officers found fires in three different locations. The fire department put the fires out, but couldn't determine the causes. Firefighters then found seven more fires on FM 78 headed toward San Antonio. All the fires reportedly appeared to have been intentionally set. Police say they've found a person of interest in the case.