The license says, Texas, but according to the news (CNN, Fox, MSNBC etc.) he had a home in Mesquite, Nevada.  There are a number of towns named Mesquite (one of then in New Mexico and one in Colorado, too) so it's possible it's different guy with same name living in a town with the same name but different state.  As far as it being "critical information"  I suppose it would help track down more information about the man who did the shooting. I saw on MSNBC a "interview" ( the guy came half way out of his front door) a man who says he is his brother. Claims his "brother" was a "well to do" guy who had no real politics, religion, or mental condition that could account for why he did this. 
If it really was him hunting or fishing (Salmon Falls Resort is a VERY expensive place) the guy must have money because it isn't cheap !
Why does this all matter ? I suppose some forensic profiler or forensic psychiatrist will want to know to try to figure what made him tick and why he did it.