It is shown for the first time that the chirping Alfvén instabilities observed mostly during ICRF heating have been positively identified as energetic particle modes (EPMs). This has been possible because of a detailed measurement of the q profile with the MSE diagnostic in DIII-D. The EPMs are shown to be the leading cause of the monster sawtooth crash. It is also shown that toroidal Alfén eigenmodes are excited either directly or indirectly by the EPMs and that they cause fast ion losses. A scenario for the stabilization and the crash of the monster sawteeth and for the degradation of the ICRF heating efficiency at high power is presented.