Differences AB, BC, and CA are {0, -5, -4}, {2, 6, 1}, {-2, -1, 3}, respectively. The lengths associated with these differences are
... √(0² +(-5)² +(-4)²) = √41
... √(2² +6² +1²) = √41
... √((-2)² +(-1)² +3²) = √14
Two of the legs of the triangle are the same length (√41), so the triangle is isosceles.