Fighters responded to reports of a palm tree on fire along the railroad tracks near Lambert Road and 1st Avenue just before 8 p.m. Thursday. They then called in police, saying they saw a man with a blowtorch trying to set more fires.
A photographer in the area wound up spotting the suspect and followed him until Whittier police arrived.
The man was arrested on suspicion of arson. Police say they will be back in the area Friday to collect video evidence of the suspect.