Justin Bieber lost his cool with a paparazzo today as the photographer allegedly blocked the pop star's car as Bieber and girlfriend Selena Gomez tried to leave a movie theater in Calabasas.

The pap called 911 and complained of pain in his chest. Our photographer who was there, tells us Bieber's bodyguards said JB was "using the moves [I] taught him."

Bieb's bodyguard scuffled with a paparazzo at LAX back in February when a photographer reportedly refused to stop taking pix of the star.

Justin lost his shoe in the today's altercation and Selena tried, unsuccessfully, to intervene. After the incident, the police were called in, as was an ambulance. It's unclear whether either side will press charges.

Demi Moore and Ashton Kutcher weren't feelin' the love for photographers last night after they emerged from the Arclight movie theater.

Ashton couldn't bring himself to put a smile on his face and Demi couldn't even bring herself to show her face ... in fact, when asked why she wouldn't answer any of our questions, she said, "Because you're f-ing a-holes."

That's the spirit, Demi!

Orlando Bloom was NOT in the mood yesterday as photographers snapped him arriving home on his motorcycle.

Orly jumped off his bike, immediately began yelling at a couple of the guys and even ducked into one shooter's car ... to grab some equipment maybe? It wasn't clear what he was doing but when he got in in a photographer's face and reached for his lens, it was pretty obvious he was trying to get that guy outta there!

Our photographer watching from the side tells us: "Orlando was super pissed. He has his moments -- he just gets upset sometimes and doesn't want photographers around. No one was doing anything other than standing on the side of the road taking pictures, but he just didn't want it that day."

Obviously the paps are staked out trying to catch a glimpse of Orlando's pregnant fiancee Miranda Kerr, who's due next month.

Hey, everyone's allowed to be in a bad mood sometimes but Orly, relax, we love you!

This is a WILD story ... Robert Pattinson left a house party in Malibu last night around 8 pm PT (with guitar in hand) and not only backed into the car of a fellow party-er but then pulled forward and hit ANOTHER car and then ... DROVE OFF!

Pattinson's super cool vintage ride suffered minimal damage and the other cars both had dents and scrapes but that didn't bother Rob one bit -- he left the scene without leaving a note on either car or telling anyone what he'd done.

RPatz headed south down PCH and after driving for about 20 minutes, he stopped and yelled at the photographers to leave him alone. He then went OFF on one of our guys (VIDEO COMING SOON!).

Rob gave up, got back in his car and drove off. A few miles later, when he saw police on the side of the road, Rob pulled over and spoke to the cops and asked them for help with our photographers who were behind him and they said there was nothing they could do. Meanwhile, fans gathered and started taking pix too - it's not just us, Rob; sorry!

Pattinson continued and hit up Soho House to finish off the night.

We have to say, we've not seen this side of the Twilight vamp before. Pattinson was outta control and upset. His quite, sensitive side went out the window and we discovered Jekyl!

Police arrived at Lindsay Lohan's apartment just a while ago and were questioning photographers outside the buildling. A few snappers were even taken aside for a private conversation with sheriffs.

In fact, one deputy even got in on the action, giving a photographer a dose of his own medicine and turning the camera on him!

Sergeant Conner at the West Hollywood Sheriffs Department tells X17online: "We had a call related to the paparazzi outside the building. Apparently someone tried to rush the building but it turned out to be a non-event."

In fact, it's not only the "paparazzi" there, but the mainstream "paparazzi" as well -- local news vans have been outside off-and-on all day after Lindsay was sentenced to 90 days in jail yesterday, for violation of probation connected to her back-to-back DUIs in 2007. Lohan is set to turn herself in July 20.

This is better than grainy tape of thieves caught by a security camera, this is Transformers mega-star Shia LaBeouf caught by an X17 videographer stealing the same snapper's camera lenses! What was Shia thinking???!!!

Shia LaBeouf has returned the camera lenses to police who gave them back to the photographer. But our shooter wasn't fully satisfied ... he asked LAPD Sgt. Gottschalk why Shia won't be arrested when a photographer who had done the same would be in handcuffs within minutes. Gottschalk replied, "We handle each incident on a case-by-case basis."

An X17 photographer was just a victim of Shia LaBeouf's wild temper as the Transformers star came to our snapper's car outside the actor's Hollywood Hills home and snatched some camera equipment out of the vehicle!

Shia then ran back into his home and appeared to have no intention of returning the $3000 camera lenses. Further, LaBeouf then called the police to complain about the photographer.

Well, that backfired -- The cop made the actor return the equipment and we're told the brazen actor then walked away with his tail between his legs ...

A policeman is still inside Shia's house right now -- more details and VIDEO coming! ...