How did Claudius Eutychus die?

Do you like the old Roman mysterys?
Then perhaps this one is for you.
The buisnessman Claudius Eutychus has been found dead in his home, his mouth is black, his clothes is bloody.

You can investigate many clues in the room, a bloody scalpell, a sleeping dog, a letter of buissnes.

The eyewittneses is eager to tell you what they seen, but is they talking the truth?