Oh, Justin Bieber. Just when he seemed to be shaping up and behaving a bit better -- even potentially winning Selena Gomez over one more time -- he's in trouble again.

The 'Baby' singer's tour bus was busted for pot in Sweden. What happened?

TMZ reports that a police officer said he smelled marijuana wafting from Bieber's bus, which was parked in front of the Grand Hotel in Stockholm -- the same hotel he left with Gomez in tow earlier this week. The officer called in a special narcotics unit to instate a search warrant. Officers from that narcotics unit are who later caught up with the bus at Bieber's tour stop that night.

Swedish police reportedly boarded the bus when it pulled into and parked at the Globe Arena in Stockholm late Wednesday night. No one was on the bus when police searched it.

Cops found a small amount of marijuana on board, but since no one was actually on the bus at the time, no one will be charged -- because it's virtually impossible to tell whose weed it actually was. The marijuana was found on the floor of the bus, so there's no indication of who brought it on board.

TMZ noted that Bieber was seen with Lil Za earlier that day ... the same guy with whom he was photographed smoking weed at a party.

Police also found a taser on the bus.

This isn't Biebs' only drama this week, either. Radar Online reports that he threw a tantrum at a fragrance shoot. Bieber allegedly arrived six hours late to the photo shoot and refused to wear the costume that had been agreed upon and arranged.

"After showing up six hours late, Justin threw a temper tantrum because they wanted him to wear a bell boy hat — but he refused,” a source said. "This kid is quickly is quickly getting a reputation as someone that no one wants to work with. It was disgraceful.”

What's more, Bieber kept fans in Copenhagen waiting for an extra hour and a half for his performance because he was playing ping-pong backstage with his dancers.

Bieber's attitude is rumored to have continued when he and Gomez went to dinner at a fancy restaurant -- and he refused to tip the waiter. Yikes! Per a source, the pair went to “a very upscale restaurant on Friday night for a free meal and even though the meal was complimentary, Justin couldn't be bothered to tip the hard working waiter. It was very low class and just disrespectful. Selena acted like a true lady, but Justin acted like an entitled punk.”

To be fair to Bieber in the case of the dining out ordeal, he may not have been aware of the need to tip if the meal was free -- and other nations have different tipping systems (many don't practice it at all), so when you're on an international tour, it can be easy to get confused and forget where you are. But dude, here's a tip: It's always better to err on the side of generosity!

Watch the Justin Bieber 'Beauty and a Beat' Video