Former CIA agent charged with years of spying for China

From the article:

— The FBI conducted an undercover operation in January 2019, during which an undercover officer allegedly claimed to be working for Chinese intelligence services and showed Ma a video recording of a 2001 meeting. -

I’d love to know how they got that recording 18 years later. Maybe the 85 year old co conspirator who originally flipped him? Amazing they actually kept the blackmail material into their 80s if so, if not, still curious!