"we firmly believe there are people out there who do know who this person is and could contribute,” said David Sundberg, assistant director in charge of the FBI’s Washington Field Office.

“It’s been almost four years. Allegiances change,” Sundberg said.

https://www.wsj.com/politics/national-security/fbi-seeks-leads-in-mystery-of-pipe-bombs-found-on-jan-6-015a2e9d