[piasa]

This sensible reporting from a site in India may give a clue on his motivation- a possible case of a spurned love interest? :

"A gentleman, who walked in through the front door, shot the girl that was right behind the counter," said Holden Harrah, who witnessed the shooting. -----https://www.outlookindia.com/website/story/13-including-gunman-dead-in-mass-shooting-at-bar-in-california-us/319778

[piasa]

...Or she was just the first person he saw.