We investigate the solar origin of near-relativistic electrons and protons during the X17.2/4B flare as observed by the Comprehensive Suprathermal and Energetic Particle Analyser (COSTEP) and Three-Dimensional Plasma (3DP) analyzer experiments on board the SOHO and Wind spacecraft. These observations are combined with ground- and space-based spectral radio data obtained by the Potsdam spectrograph and the Wind/Waves instrument. Additionally, we use measurements of relativistic protons (ground-level event (GLE)) by neutron monitors (Kiel and Moscow). Timing and electron energy spectrum analysis suggest that there are three separate stages of electron injection into interplanetary space: (1) An injection of radio type III--producing electrons is observed first; (2) an impulsive injection with an almost symmetric time profile with a short duration (~18 min) is released ~11 min later, followed by (3) a gradual, long (>1 hour) lasting injection, with an onset ~25 min after the first type III burst. While the first escaping type III--producing electrons are more likely related to the reconnection processes during the impulsive flare phase, the association of the two delayed electron injections with solar events is not well understood.