There are various causes for black tarry stool (presence of the digested blood) including bleeding oesophagus (or anywhere else in the gastrointestinal tract), infections, parasites, poisoning, medicine side effects, tumours, foreign bodies (and other obstructions) or other conditions. (wagwalking.com)
There are various causes of black tarry faeces including foreign bodies, poisoning, gastric ulcers, upper respiratory tract bleed (which in turn is swallowed), eating bloody meat, severe infections and parasites. (wagwalking.com)
We thoug nothing of it until he threw up about 3 times (not all at one, whitin as spane of a couple days) i found black tarry poop i think from hesterday, but he pooped this morning and it seemed to be okay. (wagwalking.com)