Almost every shooting that happens there are initial reports of multiple shooters and they're almost always wrong.
But the question of how did he kill/wound so many people with one 30 round mag is a good one. It looks like he's wearing cargo pants ... did he have a mag in a side pocket and reload at some point?
Every Walmart has extensive video surveillance. Why has only one grainy still been released?
It is highly likely that his online persona has been meddled with. That I find completely believable. Every single shooter they try and show they were a right wing extremist, even when they were clearly not.
In my neck of the woods, I know many liberals who also own and support gun rights (to a degree). People aren't cardboard cutouts. There are conservatives who support the environment, there are liberals who like guns.