  Coronal mass ejections (CMEs) drive powerful shocks and thereby accelerate
solar energetic particles (SEPs) as they propagate from the corona into
interplanetary space. Here we present the processes of three-stage particle
acceleration by a CME-driven shock detected by the in situ spacecraft--Parker
Solar Probe (PSP) on 2022 August 27. The onset of SEPs is produced by a fast
CME with a speed of 1284 km/s when it propagates to $\sim$2.85 Rs. The second
stage of particle acceleration occurs when the fast CME catches up and
interacts with a preceding slow one in interplanetary space at $\sim$40 Rs
($\sim$0.19 au). The CME interaction is accompanied by an intense
interplanetary type II radio enhancement. Such direct measurement of particle
acceleration during interplanetary CME interaction/radio enhancement is rarely
recorded in previous studies. The third stage of energetic storm particles is
associated with the CME-driven shock passage of the PSP at $\sim$0.38 au.
Obviously, harder particle spectra are found in the latter two stages than the
first one, which can arise from a stronger shock produced by the CME
interaction and the enriched seed particles inside the preceding CME.
