Greg Biffle Home Burglary After Tragic Death Investigated As Inside Job

Sick twist to an already horrible story ... authorities in North Carolina are investigating the burglary of Greg Biffle's home, following his tragic death, as a potential inside job.

Authorities in Iredell County say the suspicious activity started just hours after the December 18 crash in Statesville, NC, which took the life of Biffle, his wife Cristina, his two kids, and three others, with a disturbing email that read, "I heard you're dead, rest in hell," being sent to the deceased driver's inbox, according to WSOC.

Around the same time, investigators say Biffle's banking passwords were changed ... and there was also alleged fraudulent activity on Cristina's Venmo account.

Later in the month, a bogus check was cashed against Biffle's account, and multiple other attempts were made.

Then, on January 7, the Biffle's mansion in Mooresville was broken into ... a crime captured on surveillance video.

The perps, according to law enforcement, seemed to know their way around the property, took $30K in cash, two handguns, jewelry, and various racing memorabilia, spending around six hours in the home.

Authorities have not yet made any arrests, and although they haven't publicly named anyone, there's reason to believe they are zeroing in on suspects.

Law enforcement has executed multiple search warrants, including at a home and a storage unit.