My GUESS:
He contracted something fatal and went off to commit suicide rather than deal with the effects.
He's smart enough to know not to do that. His body would be contaminated and leech down into the soil, or animals feeding on him would get infected and spread it, or it would contaminate officers and EMT who found and handled the body.
1) In January, he spoke out against the flu vaccine and was worried he'd "be fired or worse."
2) Also, in January, another well respected doctor, Dr. Daniel Neides, the Chief Operating Officer of the Cleveland Clinic Wellness Institute was fired for speaking out against this year's vaccine.
3) Brenda Fitzgerald, Director of the Centers for Disease Control and Prevention, was also fired in January on the pretense she had tobacco products in her stock portfolio.