Lonzo Ball's 15-year-old brother, LaMelo, unleashed a sneak water balloon attack on two girls in bikinis -- INSIDE the Vegas home where he's staying -- while wearing a shirt with his own face on it.
It all went down Sunday night -- and yeah, Lonzo was inside the home as the water fight broke out. It was a mess. Water everywhere. Ketchup. Craziness.
Unclear if Lonzo is footing the bill for the pad (probably, since he's the only one getting a paycheck) -- but he didn't seem to care as his 15-year-old lil bro destroyed the house.
There was one moment where LaMelo grabbed a loaded pillowcase and swung it at one of the women -- but smartly put it down and splashed her with water instead. Careful, dude.
Of course, Lonzo's in town with the Lakers for the NBA Summer League. All things considered, this is a pretty tame night ... as far as Vegas goes.