...which relates to the Terminator universe.
I think the Garza Murder is a temporal artifact...not a historical artifact, though, because it hasn't happened yet.
Garza's the man at the top of the power pyramid tormenting Hopper, and he'll get killed by Det. Hopper at the end of the season. But I don't think his wife's lying during this season when she says she saw Hopper kill Mr. Garza. Because Hopper did...or rather, because Hopper will.
Let's use the Terminator universe to explain...in the first movie, Kyle Reese tells Sara Connor that he was born after Judgement Day. In the Sarah Connor Chronicles, we see young Kyle Reese walking around and playing before Judgement Day. Yet John Connor (son of Kyle) remains unchanged - his eyes aren't a different colour, nor is his hair, etc.
Basically, history changes, yet one of the very things we'd expect to be changed as well - doesn't change. There might be a better word than "artifact," but I can't think of any. (my fault)
In other words, Garza's death is the result of something that happens later on...but his death also causes his murder. Just as John Connor sends back Kyle to ensure (insure?) that John Connor is born. (and just as the Model 101 Terminator is identical to itselves, no matter when Judgement Day is)
I confess, that was more coherent before I typed it. sorry.
"You did not prevent Judgement Day; you merely delayed it." -Terminator Model 101; 3rd film.