Who killed Robert Krentz?

The killing of Arizona rancher Robert Krentz on March 27 sent the state - and nation - into conniptions of anti-immigrant fervor, as everyone and his brother declared that he was killed by drug smugglers from Mexico. Now - today - the Arizona Daily Star, from Tucson, is reporting that authorities believe he was killed by a lone American:

The killing of a Southern Arizona rancher that sparked an outcry to secure the border was not random, and investigators are focusing on an American suspect, the Arizona Daily Star has learned.

The killing led directly to Arizona's new Jaime Crow law and sentiments of outrage from the state's reactionary Republicans. If the truth about Krentz's murder turns out to be radically different than that reported earlier will that really change anything, or has the damage already been done? I think you know the answer to that question.

UPDATE: It also turns out that the alleged killing of Krentz by border crossers would have been the first American killed in 10 years:

...according to the Border Patrol, Krentz is the only American murdered by a suspected illegal immigrant in at least a decade within the agency's Tucson sector, the busiest smuggling route among the Border Patrol's nine coverage regions ...

So much for Americans being mortally threatened by immigrants.