Ethan shot Aroma.

After Chris has managed to take control of everything smoothly, which surprised him. He was expecting the owner to discover at some point, but that didn't happen, which made him go to the extent of taking control, instead of just deactivating them.

After taking control, he was able to scroll the scene in the entire place. He didn't see the guys who were busy avoiding the installed cameras, but could see the scene where Aroma and Austin were fighting.

He saw the twins and realize Nathan's crew has come for rescue already. Not knowing what to do, as the place seem less dangerous for him and his crew now, he decided to go in as well.

....

Without a change in Ethan's expression, he fired a shot, which hit Austin's chest. 

Aroma's eyes widened, as she quickly held him and both slowly go down. Ethan dropped the gun and pulled Diana towards him.