Sean Simpson is a teacher at Marjory Stoneman Douglas High School who had expressed an openness the idea of arming teachers to prevent school shootings.
On Sunday, he used a public bathroom on Deerfield Beach Pier and forgot his loaded pistol in the stall. He realized his mistake after leaving the bathroom, upon hearing his gun being discharged. He then raced back to the bathroom and discovered an apparently drunk homeless man holding his 9mm Glock.
Mr Simpson has been arrested for failing to safely store a firearm, as has Joseph Spataro, the man who fired the gun, who was charged with discharging a firearm while intoxicated.
Simpson's views on guns were apparently complex; while he had cautiously publicly endorsed the idea of arming teachers, he also attended the March for Our Lives.
A spokeswoman for the Broward County School Board said the district is not expected to take disciplinary action against him, according to WPLG-TV.
On Tuesday, the Broward School Board unanimously rejected the state's new programme to arm school staff, according to the Miami Herald.