Plots of HEP fluxes 10 days prior to the flare that started at UT 09:51 on 2003 October 28. High energy particle fluxes (>5 MeV and higher) stay at low level. Precursor shows up at about UT 18:00 on October 26, i.e., about 40 hr prior to the flare, and appears as a sudden elevation of all channels including even the >50 MeV protons (purple line). The >1 MeV proton flux is shown to emphasize the absence of higher energy proton fluxes during several days prior to the precursor and flare (see the text).