The disruptive phase of the m = 1 'sawtooth' oscillations in tokamaks is examined. It is shown that, depending on the shear, the disruptive phase could be related either to an m = 1 island filling the plasma core or to the growth of large-scale stochasticity surrounding the island which is generated by the interaction of the island dynamics with the perturbation. The latter situation, associated with high shear at the q = 1 surface, and, therefore, low q on axis, is characteristic of some recent experiments. In particular, it is shown that the observations of q = 1 sawtooth oscillations reported in TFR are consistent with the development of a large stochastic layer. There are no adjustable parameters in the theory; reasonable values are assumed for those quantities that are not known precisely.