Varga was dead.
Snape told Tris early the next morning, the day after the incident.
When Tris was summoned to the Potions office, he thought he had done something to annoy his Head of House. Instead, he was given this news.
"Mr. Varga refused to cooperate with the Ministry of Magic, so the Ministry chose to use Veritaserum on him. Something interesting happened." As Snape said this, the corner of his mouth actually curled slightly, as though it really was interesting.
"The instant Mr. Varga drank the Veritaserum, his intestines ruptured and his innards rotted, killing him. The Ministry didn't even have time to treat him. Most of them are useless, of course, but Scrimgeour himself was present, and even he couldn't act in time. That suggests the poison took effect rather quickly.
"Very interesting. A dormant toxin capable of reacting violently with Veritaserum..."
Toward the end, Snape began muttering to himself.
Clearly, compared with Tris being marked and someone dying, he was more interested in a poison that could react with Veritaserum and take effect so violently and rapidly that even a wizard of Scrimgeour's caliber couldn't stop it in time.
I always knew you were unreliable, but did you have to be this unreliable?
Watching Snape seemingly sink into thoughts about potions, Tris was speechless for a moment before asking tentatively, "Professor, if there's nothing else, may I go?"
Snape waved a hand, as though shooing away a fly that was disturbing his thoughts.
Tris fought down the urge to roll his eyes and swear, then turned to leave.
"Oh, one more thing!" Snape suddenly spoke.
Tris stopped and looked back in confusion.
"That business with Quirrell last school year." Snape raised his eyes, seemingly mentioning it in passing. "I handled the cleanup and found one of Quirrell's