Like a modern-day Helen of Troy wearing a diaper, tiny singer Ariana Grande started a war last night.

It began when freshly-roasted Justin Bieber joined her on stage at the Forum in Los Angeles, according to TMZ. While the two performed "As Long As You Love Me"—a song originally recorded by Bieber and Big Sean, Ariana's boyfriend—Big Sean watched from the audience.

Here's the bad thing that happened:

Justin Bieber (not Ariana Grande's boyfriend) embraced Ariana Grande (Big Sean's girlfriend) in a manner that some would describe as romantic, and others, disgusting!!!!! TMZ's video of the performance shows that Ariana wriggled free from his grasp, but not soon enough.

For Big Sean saw. (Justin Bieber touching his girlfriend.)

What's going to happen now? More bad things, probably. Big Sean tweeted (and then deleted, doy) after the show last night: "This kid about to learn not to touch my girl like that. Beliebe that."

Justin Bieber responded with a :)

So, I guess this is how everything ends, with Big Sean murdering Justin Bieber. It's comforting to know that since Ariana is so little now, she'll barely remember all of this when grows up.

Photo via Splash News. Contact the author at allie@gawker.com.