What does a fist bump from the boss mean?

So my boss only ever talks to me to critique my work. Almost all of the employees get lectured and he never, ever, gives a compliment or thumbs up to any employee.
About three weeks ago he asked me to work later and then gave me a high five in front of the new hire, which I still believe he did to make himself seem cool in front of him. But then last week he tells me to keep doing what I was doing at work and gave me a fist bump. A few days later, before he leaves, he gave me a fist bump. After I was having a bad day the next day and he had gotten onto me for a few things, he gave me another fist bump and held intense eye contact until I gave him one back. Now today, before he even says hi or I'm settled into work with my co-workers, he came up to me and gave me a fist bump (not the others) before going back to work.
So does this mean he thinks I'm one of his favorite employees? Or is this some weird flirting thing?

What does a fist bump from the boss mean?
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