Last night (June 4), Ariana Grandereturned to perform in the city of Manchester, England for the first time since the May 22 suicide bomb attack outside her show at the Manchester Arena that claimed 22 lives, many of them children, and injured more than 100 others. And she didn't come alone: Just 13 days after the terrorist attack, Grande and her team, led by manager Scooter Braun and backed by Live Nation, put together "One Love Manchester," an all-star benefit concert that drew an audience of 55,000.

Organizing a high-profile concert in under two weeks is daunting enough -- many victims of the original attack are still recovering in hospitals, and the evacuation of the Rock am Ring festival in Germany on Friday (June 2) and the terrorist attack in London on Saturday (June 3) only added to the pressure. But the concert drew an impressive lineup -- Grande was joined by Justin Bieber, Katy Perry, Coldplay, Liam Gallagher, The Black Eyed Peas, Take That, Robbie Williams, Niall Horan, Miley Cyrus and more -- and ultimately raised $3 million for the British Red Cross during the concert alone.

This morning (June 5), just hours after the show's conclusion, Braun spoke with Billboard about the process of pulling the benefit concert together, the concerns that made it especially challenging, and the moments that made it what will surely be one of the most important musical events of the year.

Congratulations on last night. How do feel this morning?

Scooter Braun: Surreal. Everyone’s saying it’s a big success and everything, and my feeling, honestly -- I have this weird feeling that there are tough times ahead. But I’m so happy that what we did last night is going to be a kind of symbol of hope that I think people can turn to the next time, so we can defeat [evil] and win. I’m actually more grateful than anything. The response from Manchester just blew my mind.

Where were you when you first heard about the Manchester bomb attack?

When I first found out, I was at a board meeting in L.A. and literally was about to go to the airport to go to London. My first thought was, “What is going on?” There was a lot of different information coming in in a very strange way and we weren’t sure what was real and what wasn’t. When it finally came through what had actually happened, my initial reaction was sadness. But then it quickly turned to anger and, “We need to fight.”

What were the most memorable moments of last night's benefit concert for you? 

I get emotional just thinking about it. From the moment the idea [of the benefit concert] came I was very obsessed with it. And at first I had to slow my mind down because Ariana -- rightfully so -- she didn’t know if she could ever go on stage again. And then two days after she called me and she goes, “Look, I need to do something. I keep thinking about it and if I don’t do something I feel like they might have died in vain. So what’s the idea?” I tell her and she goes, “Okay, I’m in.” To go from that point and for her to trust me like that, I’m eternally grateful. And then for her to let me throw it all on her shoulders, her courage and bravery is just amazing.

But the night before, [the terrorist attack in] London happened, and we put our statement of resilience out saying, “There’s a greater purpose here. Now it’s even more important to honor London and Manchester.” And the police put out a statement -- because they had to -- saying, “We’re going to try and protect you the best we can, but the terror levels are critical,” meaning it’s highly likely an attack will happen, so please be vigilant. That was the quote. And I think to myself, “We’re broadcasting this on the BBC, YouTube, Facebook, Twitter. It’s being broadcast in 40 countries around the world. These people in Manchester can sit on their couch in the safety of their homes and they don’t need to show up. There’s no way people are coming.” And when we started the show and Marcus Mumford took the stage, there were 55,000 people in there -- sold out and full. He led the moment of silence and right before he played it was completely silent and he said, “Let’s not be afraid.” And there was a roar in the crowd that literally will give me chills for the rest of my life.

There were so many amazing moments: Ariana and “Somewhere Over The Rainbow,” which was spectacular; Justin getting emotional; The Black Eyed Peas; Liam Gallagher; Coldplay. Just one after another after another. Take That, Robbie Williams, Miley Cyrus, Katy [Perry] when she did “Roar.” Everything was amazing, but the best performance of the night for me was, when the show ended, something magical happened. During Robbie’s set he kept doing this thing with the crowd singing, “Manchester, we’re strong. We’ll keep singing our song.” When the show was over and all 55,000 people had to leave they started singing and getting louder and louder to the point where it became a roar of people singing, “Manchester we’re strong.” The city of Manchester was the hero of the show.

What was the most challenging part of producing the show and pulling it off? 

Just the constant doubts and the repetitive no’s. “No, there’s no way this can happen. No, we can’t pull it off. No, you shouldn’t be doing this, it’s too soon.” We didn’t care. The first thing I did was reach out to the family liaison [team], explain the idea and say, “I just want to know if I have the support of the families.” The families came back with an overwhelming yes. I got that answer within 24 hours and the moment that happened we were on a mission. You couldn’t tell us no.

During the show, Ariana spoke about how meeting the mother of Olivia Campbell, one of the victims who died in the arena attack, helped decide the upbeat tone of the concert. Was the plan originally for a more somber and reflective set list? 

Everyone was very sensitive about paying respect to the victims and that was [Ariana’s] biggest concern. We met with 15 of the families one by one on Friday night and Olivia’s mom was the last. We were talking with her about the show and she told me what songs were Olivia’s favorites and she said, “We need to play the hits. That’s what Olivia would have wanted.” That gave Ariana the courage to say, “This needs to also be a celebration of people.”

What did you do or say to Ariana to help her get through the past two weeks?

I just told her that I’m not going to leave her side. I’m not going to go anywhere. We’re all in this together. Everybody told her that we will be with her every step of the way -- whether that’s going with you to the children's hospital or meeting the families -- that she didn’t need to take this on alone and that we would all be there with her. She was so courageous and I’m incredibly proud of her. But I’m also proud of all the other artists -- especially after London, they could have easily said, “Hey, let’s just give it some time.” And every single one of them not only said, “We’re in,” some of them called me to say, “You’re not cancelling, right? Don’t cancel.”

Did you seek any advice or guidance from any of your mentors before traveling to Manchester? 

It’s the music business, so no. I just said I was going to do this and the biggest thing was people telling me I was doing it too soon. But that’s the beautiful thing about music -- there are no rules. The only rule in the music business, in my opinion, is that you follow your heart.

How are you coaching Ariana moving forward from here?

She’s the one who says, “After this, we all need to be kinder to each other, show more love to each other and we have to be stronger for each other.” Because for those people who passed away and those children who passed away, we have a responsibility to them now to be brave.