The Electron Proton and Alpha Monitor (EPAM) onboard the Advanced Composition Explorer (ACE) spacecraft detected a Solar Energetic Particle Event (SEP) on 2015 October 29. The EPAM telescopes detected near relativistic electrons, and protons with energies above 1 GeV. Although no statistically significant enhancement in the count rates of neutron monitors near sea level was observed at that time, there were simultaneous significant enhancements in the count rates of at least two differently located high-elevation neutron monitors. Therefore, this event is not classified as a Ground Level Enhancement (GLE) but as a sub-GLE. The flare related to this event was very likely behind the limb, which implies that a flare origin for these particles can not be excluded, but ground based radio observations show that this event is also accompanied by type II and type IV emission so a different source for the particles is possible. Using a detailed model for particle propagation and interaction with the EPAM detectors, we discuss the possible association of the detected particles in situ with the flare, the shock, and the restructuring in the aftermath of the Coronal Mass Ejection (CME) associated with the event.