again, occam's razor.
it's unlikely to be a robbery gone bad. most thieves are cowards and wouldn't dare approach a group of two or more. it is also unlikely that they would shoot them, since a robber is in it for the money and (generally) doesn't want blood on his hands.
it is also incredibly unlikely to be a psychopath, or else there would be an ongoing chain of murders.
it's not a sex crime, they weren't raped and they weren't prostitutes.
besides that I can't think of a lot of reasons to randomly shoot two people. easy to assume it's a hate crime. you don't kill people without a reason, even if your reasoning is bad.
it's horrible regardless, but still.
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maybe, lol