How was Mr. Robner killed?

Hint 1 of 17:

First off, he did not die of an overdose of Ebullion.

Hint 2 of 17:

Someone gave him a medicine that, when mixed with the medicine he was taking,
would provide a fatal result.

Hint 3 of 17:

Look around for types of medicine.

Hint 4 of 17:

That LoBlo in Ms. Dunbar's medicine cabinet in her bathroom looks suspicious.

Hint 5 of 17:

Examine the label.  Whoa, it could be possible!

Hint 6 of 17:

Now, you'll have to wait until 11:30 or so to talk to McNabb.

Hint 7 of 17:

Ask him what's wrong (type MCNABB, WHAT'S WRONG?)

Hint 8 of 17:

He'll show you some odd looking holes in his garden.