CR's immigration status is considered as 'fact'. IMO, that matters in this case only to this point: a motive for murder. When MT warned CR she would "call the police", he panicked for fear of being found out as having entered and living in the country illegally and his 'explosive' nature (as one or more CR acquaintances have described) led him to doing the only thing he thought he must do to prevent MT from making good on her warning.
Reading and interpreting what people who know/knew CR, either closely or in-passing at parties, etc., it seems he displayed little to no self-confidence, was mostly quiet, shy, seemingly disengaged or self-focused and that some girls/women were drawn to his appearance and realized the outside packaging didn't wrap a maturity capable of understanding or handling it. It was easy for him to present the appearance (hair, trimmed beard, slim and somewhat athletic) but that is where it ended. 'All look and no hat', to adopt a familiar phrase.
It is described (by those same people) that CR hung around mostly with the other male workers. I assume CR had become frustrated many times in his teen/adult life when he attempted to interact with girls/women in general, and even more frustrated when he felt the urge to engage with girls/women that 'piqued his interest' (I'm using a family-friendly phrase to describe what we all know it to be).
Frustration and confusion eventually led to desperation, and ultimately, anger when his misguided attempt to engage MT blew up in his face. That ultimate humiliation plus the fear of being found out (MT's warning she would call LE) led him to committing a heinous crime and unfortunately, MT had to suffer at his hand while her family, friends and quite frankly, many of us at Websleuths are left to suffer for CR's mental inadequacies and eventual criminal behavior.
MT was at the wrong place at the wrong time. This crime is not her fault, though, as this being a free country MT had every right to be where she was and to have been doing what she was doing. It was CR who had no right to be where he was and no right to do what he did.
MOO