MTV News spoke to Maejor about working with the 19-year-old on the R&B-tinged ballad, which Bieber penned while on tour.
"He wanted to write a song about things he's been going through with his relationship and everything. And I think that's one of the best songs to come out," he explained, shouting out Chef Tone and T Minus, who contributed to the track. "So we just got in and zoned out and created 'Heartbreaker.' "
Bieber tries to make amends with a former flame on the slow jam. "We brought in real harps, guitar players like it's really a lot of music in there. It's not just the cheap, try and hurry up and just do a quick song and make some money," he said. "We tried to create a masterpiece with that."
The lyrics that made the final cut are reflections of real conversations Bieber had with his team while creating the track.
"It was called his 'journals,' so we wanted to make this music the most honest as possible, so really, all the conversations in the studio are heard in the song," Maejor explained. "Everything that was said we tried to capture all those moments in the music, and I think that's why it came out so honest and so personal."
He continued, "I think it's cool, him especially being that age at 19, being a dude a lot of times people think that's not cool to show real honesty and I think that it's brave of him to do that. I was happy that he decided to do that ... so I honor his bravery in doing that."
Maejor also revealed that the song's spoken-word bridge took some convincing to include on the final cut.
"We kind of broke the format a little bit by putting almost a poem with him speaking in the middle of the song. A lot of people were against it 'cause it doesn't fit normal radio standards," he said. "But it was the most honest part and it just felt natural in terms of the music and for that we tried to forget all the rules."
Regardless of whatever inspired the track for Bieber, Maejor thinks the song has a mass appeal.
"It was pretty much everything of how he was feeling at the time and the good thing about music is people can relate that to any moment of their life like people are heartbroken over the loss of someone it doesn't necessarily have to be about love but whatever's going on [and] people can relate to that through music," he said.