Still seems like a lot of info is missing, but from the linked article:
Arce has been working toward legal citizenship
The event is fucked up (I assume—there is no info about anything causing him to be targeted specifically, but he has teenage children, obviously he's been in the US for some time now), but at least, based on this, "legal immigrant" in your title is not accurate.
It's important to be honest and accurate, or you make it easier to be dismissed by opponents.
Edit: It's hard to find more information, but apparently he immigrated illegally in 2004, and ignored a deportation order from 2005 (so, has been in the country illegally for over 20 years). If that's true, then yeah, "legal immigrant" in the title is a straight-up lie.