An off-duty Kansas City firefighter was killed in a shooting Thursday afternoon at an Independence gas station.Independence police said they were called about 2:30 p.m. to the Liquorland gas station near Sterling Avenue and U.S. 40 Highway.An eyewitness who asked that KMBC not show her face said the firefighter heard a man disrespect a cashier inside the store.She said the firefighter spoke up in the woman's defense. That started an argument.The argument grew into fistfight. The witness said the man fighting with the firefighter came with a woman and that woman may have pulled the trigger of the gun. She said the firefighter was shot outside the store and then he came back into the store for help.When officers arrived, they say the firefighter had already died."Unfortunately I saw everything. I saw everything and the truth is, it's very sad. For me to witness it - a death. It's one thing to talk about but it's another thing to see it," the witness said.A spokesman for the Kansas City Fire Department confirmed the victim was a firefighter. On Friday, Independence police identified him as 41-year-old Kansas City, Missouri resident Anthony Santi. Investigators said a short time after the shooting, two persons of interest were taken into custody.The investigation continues.Kansas City Mayor Quinton Lucas released a statement:"I am heartbroken to learn of the passing of a Kansas City firefighter earlier today in a neighboring community. My thoughts are with his family, friends, and all members of the Kansas City Fire Department."