A mess
The greatest mistake their group made was panicking. He couldn't blame the girl who got bit for screaming, but the scream seemed to infect all of the recruits and made them run like headless chickens.
Without investigating the situation they started running around, which resulted in a few more recruits getting bit.
Nero wasn't ashamed to admit that the sudden chaos affected him as well, but it was only for the briefest of moments. He quickly gathered himself, identified the situation for what it was. If they were near the snake's burrow, then getting them to retreat wasn't possible. They'd have to fight them all.
An initial analysis seemed to indicate that their ability was stealth based, but that did not mean that they didn't have other abilities as well. They also boasted mundane physical attributes but that might not be true for all of them.