Bottoms up! Justin Bieber, 21, shotguns a beer with friends at a party in Las Vegas and posts the video to Instagram

He just turned 21 in March, but the singer already seems to be enjoying adult life to the fullest.

Justin Bieber decided to celebrate with some friends by consuming some adult beverages at a party in Las Vegas on Saturday.

Apparently in Vegas for the Floyd Mayweather versus Andre Berto fight this Saturday, the Biebs decided to party before the fight begins and posted a video showing it on Instagram.

Drink up: Justin Bieber decided to celebrate with some friends by consuming some adult beverages at a party in Las Vegas on Saturday

Rock on: While his image has not been one of an innocent young star for awhile, this certainly sets a precedent, one that will be seen by his more than 38.4 million Instagram followers

Bieber won't be getting in trouble as he's of legal age to consume alcoholic beverages.

While JB's image has not been one of an innocent young star for awhile, this certainly sets a precedent, one that will be seen by his more than 38.4 million Instagram followers.

There was a bit of a lighter side of the already infamous post however.

Caught red-handed: Bieber has been spotted drinking alcohol many times before while he was underage (here he was 19)

Bieber apparently attempted to down the beer using a method colloquially known as 'shotgunning a beer' where one punctures the can and then uses that opening to quickly imbibe the contents of the can. 

He appeared to shotgun his beer with his friend and Shots startup founder Sam Shahidi, whom he then mentioned in his Instagram caption after losing the drinking 'race.' 

'I lost but I didn't go to college @sammy'

Shotgunning beers is of course a very common occurrence at American colleges and universities. 

Drinkin' buddies: He appeared to shotgun his beer with his friend and Shots startup founder Sam Shahidi, whom he then mentioned in his Instagram caption after losing the drinking 'race'

Self-deprecating: Justin admitted 'I lost but I didn't go to college @sammy'

As though he hadn't already fomented enough controversy, his previous Instagram post from just a few hours before showed JB with his arm around a pre-fight Floyd Mayweather.

He captioned the snap: 'Like always, I’m supporting @FloydMayweather tonight live on PPV.' 

Some followers have already taken to social media to vent their frustration at Bieber for supporting the undefeated boxer, who has had numerous brushes with the law surrounding domestic violence disputes.

'Congrats on a great win': The Biebs gave the victor Floyd Mayweather a proverbial pat on the back

Working: JB performed at a fundraiser telethon on Friday in Los Angeles to benefit the Think It Up education initiative before heading to Las Vegas