The spatial rogue waves (RWs) generated by a wide Gaussian beam in a saturated nonlinear system are experimentally observed. Our observations show that RWs are most likely to occur when Gaussian light evolves to the critical state of filament splitting, and then the probability of RWs decreases with voltage fluctuations. The occurrence probability of RWs after splitting is related to the nonlinear breathing phenomenon of optical filament, and the statistics of RWs satisfy the long-tailed L-shaped distribution. The experiment proves that the presence of high-frequency components and the aggregation of low-frequency components can serve as a prerequisite for the occurrence of extreme events (EEs).