Justin Bieber 'Heartbreaker' Released: Beliebers React to New Song 2013 on Twitter, 'Baby' Singer Explains Songs Meaning as Part of Music Journals Project [LISTEN]

Last night (Oct. 6), shortly before midnight EST, Justin Bieber released his highly anticipated new single "Heartbreaker." The mature, R&B ballad marks a new era for the "Baby" singer, as it was the start of Music Mondays and his music journals project.

As a part of the music journals, Bieber wrote a short explanation of what "Heartbreaker" means to him, published alongside the song on iTunes and on his official website (which recently got a makeover to make way for his Music Mondays).

Read what Bieber has to say about "Heartbreaker" below.

"It's a song for people going through a heartbreak -- like I was when I wrote it. It means so much to me to be able to share what I was, and still am going through, with my fans. I'm very proud of this song and I hope it gives my fans some insight into my heart. -JB"

"Heartbreaker" is reportedly about Bieber's "Stars Dance" Selena Gomez. Listen to the new single below.

Bieber's massive, dedicated fanbase were heavily promoting "Heartbreaker" before its release, and have heavily reacted to the song on Twitter since it came out, making #heartbreaker trend several times throughout the day. "I'm listening to heaven right now. #heartbreaker," wrote @OurCanadianHope. Meanwhile, @myavonheart appreciated the honesty in "Heartbreaker." "Justin is putting his story in those songs, and it warms my heart that he trusts us enough to let us hear those songs. #heartbreaker," she wrote.

Due to the support of Beliebers and the hype surrounding the single, "Heartbreaker" reached No. 1 on the iTunes singles chart upon its release.

"Heartbreaker" is the new song from Justin Bieber, and the first release as a part of his Music Mondays project, wherein he will release a new single every Monday until Dec. 9. The second Music Mondays track has yet to be revealed.