The heavily-publicized memorial service is over, the body has been buried and the press coverage of the star-studded event carries on. But aren’t we all forgetting something?

Like the fact that we still don’t have a real, definitive answer on what killed Michael Jackson in the first place? Jackson’s official death certificate says the cause of death is “deferred,” which means they simply haven’t figured it out yet.

“We have to keep some secrets,” Chief William J. Bratton of the LAPD played his cards close to vest when questioned on Tuesday. And though Jackson’s body has been released to the family following the official autopsy, not all of his organs have been given the same treatment.

Assistant Chief Coroner Ed Winter says Jackson’s brain is still being studied and tested, not to be released until some lingering questions are answered. “As soon as we are done with the brain, we will return it,” he explained, adding, “there is a whole series of tests that will be done.”

While this may sound gruesome, it’s common practice for certain samples and even entire bodily organs to remain in custody for testing when a suspicious death has occurred. Jackson’s brain will be given to his surviving family members once officials have completed their reports, which could still be weeks away.

In the meantime, what killed Michael Jackson? The answer is, we still don’t know.