Justin Bieber has recently displayed some bizarre new behavior while traveling on his Purpose tour.

At his concert Saturday night, the “Sorry” singer started to cry as he sat on the edge of the stage, and on Sunday photos surfaced of Bieber trolling a park in Boston barefoot. The star shared a snap of his new face tattoo, and on Tuesday, he proclaimed he would no longer take any pictures with his fans. He reappeared in the park on Wednesday to sit alone in a tree before his concert. TMZ also shared video of the singer partying on Wednesday night, taking shots and walking on top of the bar.

A fan posted a video of Bieber rejecting a photo and another fan posted him sitting in the tree and stretching.

Bieber’s actions are similar to the types of behavior that other Hollywood stars like Amanda Bynes, Britney Spears and Charlie Sheen have demonstrated before a big breakdown.

Dr. Keith Ablow, Fox News contributor and psychiatrist, said Bieber’s behavior seems like a downward spiral.

“It’s very hard to ‘read’ the psychological state of celebrities from a distance, because they can be doing very unusual things, in order to garner headlines,” he explained. “But, certainly, anyone with psychiatric expertise [wouldn't] hesitate to label walking around barefoot or snapping selfies in Boston Garden or getting another tattoo as signs of an impending downward spiral. It is also the case, of course, that substance use (not that I know of any substance use by Justin Bieber) can also masquerade as other mental illnesses.”

However, some experts say Bieber’s behavior is not in the same category as other stars who have had headline-making meltdowns.

“It’s not even close to the old Britney Spears and Charlie Sheen meltdowns, and they survived just fine,” said PR expert Marc Marcuse. “…. I think his personal psychology is the question. But it’s looking more and more like Justin Bieber is the Vanilla Ice of the 2010s. In fact, they’re actually starting to look alike."

And longtime Hollywood PR guru Howard Bragman, who is in touch with Bieber’s manager Scooter Braun, told FOX411 that the singer is doing better than he was a year ago.

“I know his manager has stepped in a lot and Justin is a thousand percent better than he was a year or two ago,” he said. “So I think what his manager has to do is kind of call the shots. Call his shots and say ‘when do I step in and say something and when do I let go?’ Walking around barefoot, who cares? A tattoo on the face, I might have said ‘really?’”

Bragman—who manages top Hollywood clients— said Beiber’s decision to avoid photos may be his way of establishing his maturity.

“Justin has had a roller coaster of good and bad and I think Justin is coming to his own in terms of maturity and frankly if he doesn’t feel like taking a picture then he probably shouldn’t at this point in his career. It’s probably healthy for him to say no sometimes when situations like that come up.”

Marcuse added that since Bieber has never heard the word "no," he feels entitled to a certain freedom.

“Justin became rich and famous at a very young age, with no one to tell him no,” he noted. “So he feels like a superhero, invincible. If he feels like climbing a tree, he’s just going to do it. Who’s going to stop him?”