I can't see the motivation for these attacks other than mistaking Sikh's for Muslims. In the US they stereotype Muslims as wearing turbans when few Muslims do that's why they call them towel heads.
Look at this Family Guy clip
Hadji, a Sikh character from Johnny Quest is stopped at security they are implying he is a terrorist because he has a turban.
gun control anyone ? yeah cos that will happen
makes thread, walks away backwards very slowly, awaiting racist comments and jokes..
Elections coming up soon I'm sure they will exploit these tragedies.
Unless this shooter has something personal against a particular person in the temple why would he attack a Sikh temple.
Otherwise I can only think he has confused them with people from another religion. Most likely Muslims.

What motivates someone to go into a Sikh temple, or cinema, or island retreat and kill as many people as possible?
This tbh.Well for one they're obviously totally unhinged however it's gotta be more than that. I believe the extensive news coverage surrounding these type of events really doesn't help the situation. They essentially turn into strange role models for others who wish to emulate them. News like this should be purposely localised and made as non-sensational as possible.
The dispatcher for Oak Creek Fire Department said first reports of the shooting came in about 10:30 a.m. local time (11.30 a.m. EDT).
"We do have a shooting," she said. "Our whole department is out there
Who Will Jesus Damn?
Here is a partial list from just a few scripture verses:
Jesus is my health insurance