Is a pilot responsible for CTAF announcements in this scenario?
In the U.S., the definition of an accident is covered under 49 CFR Part 830.2:  (emphasis is mine)

§ 830.2 Definitions.
As used in this part the following words or phrases are defined as follows:
Aircraft accident means an occurrence associated with the operation of an aircraft which takes place between the time any person boards the aircraft with the intention of flight and all such persons have disembarked, and in which any person suffers death or serious injury, or in which the aircraft receives substantial damage. For purposes of this part, the definition of “aircraft accident” includes “unmanned aircraft accident,” as defined herein.

From your question, this appears to clearly be an &quot;Accident.&quot;