The Black Bear Inn Murders

Between September 1st and 4th, in 2006 Christian Charles Neilsen went on a killing spree at the Black Bear Inn located Newry, ME, which resulted in the death of 4 people: James, “Jimmy”  Whitehurst (age 50), Julie Attebury Newby Bullard (age 65), Selby Bullard (age 30), and Cindy Ellen Cabral Beatson (age 43).
What could his motive have been?

Sources:
1) https://caselaw.findlaw.com/court/me-supreme-judicial-court/1377622.html
2) https://murderpedia.org/male.N/n/nielsen-christian.htm
3) https://en.wikipedia.org/wiki/Christian_Charles_Nielsen
4) https://www.findagrave.com/memorial/105419041/james-william-whitehurst
5) https://www.legacy.com/us/obituaries/sfgate/name/julie-bullard-obituary?id=25551786
6) https://www.findagrave.com/memorial/15916100/cynthia_ellen-beatson