He saw how Mara didn't let her hands move to her weapons. But it barely served to calm him in the slightest. He kept his own hands from his sabers, not wanting to draw them on the few friends he had. No doubt Mara had felt his emotions through the Force given how much time they spent together through training. He counted Mara his closest friend next to Gaia. Not to mention he felt a kinship with the woman for their similarities in life.
Hearing her questions, his mind tried to warn him that she was attempting to draw out the nature of his purpose but his heart still burned for violence since Tullius was absent. So he came up with a lie that was also the truth. "To put a kriffing end to Moriarty's men once and for all. No one else will do anything about it so I will." He regretted lying to his teacher and friend but he did not know of another way to calm his thirst for blood and vengeance.