There is no evidence to suggest that the shooting at the catholic church in Phoenix that resulted in the death and injury of two priests was anything other than a botched attempt at a burglary. A car was stolen which points to this being the case. There is no evidence to suggest it is an act of religious extremists.
The shooting was clearly related to the burglary. The shooters brought weapons because they were prepared to steal what they had came for. The priests that died were casualties. The reports show that the priests were attempting to stop the burglary from happening, but unfortunately they were unable to stop the action.
The Phoenix Catholic church shooting was only related to a burglary, because there was no evidence of anything else. Unfortunately, a burglary can go wrong, even if it has to do with a church. A lot of times, people will steal from a church parking lot, just because it is an easy target.
I think that right now a lot of evidence suggests that it was just a burglary, however when it involves the Catholic church and all the scandals that surround the church I think there is a high probability that there is more to the story. I think we will learn more about the motive as time goes on.