My first speculation when the early reports came out was this was probably a guy who shot his girlfriend or wife's boyfriend and her, then shot himself, hence the "no active shooter" report.

It wasn't until much later that they identified the shooter from security cameras, were able to identify his car, and caught him the next morning.  My next thought:  "Driving that Mitsubishi would drive anyone crazy."  Cheap, tinny 3-cylinder low horsepower car with terrible Consumer Reports ratings.

Then I thought, "All three victims were Hispanic.  Maybe this guy has had bad experience with Hispanics in the past and was blaming all his personal problems on Hispanics."  It's not uncommon for people to blame their personal shortcomings on other people or ethnicities.  The shootings appear to be random, and it could be simply because that part of Thornton has a high Hispanic population so that part of it may have been random.  But it's also possible that he was a racist.