Selena Gomez paid tribute to her longtime friend Christina Grimmie Saturday night at the Miami stop of her Revival World Tour. Gomez dedicated a cover of Hillsong Worship’s ‘Transfiguration’ to the late ‘Voice’ star, and became overwhelmed with emotion and was seen mouthing “I’m sorry” to her fans as she struggled to finish the song.

Gomez and her stepfather have successfully raised more than $170,000 for the late singer’s family. Their GoFundMe page was created on Saturday (June 11), the day after Grimme was shot and killed by an unidentified individual after her concert in Orlando. Donations have more than exceeded its initial goal of $4,000.

Gomez’s stepfather Brian Teefey was Christina’s manager, a close friend of the family’s who Teefey called “a second daughter.”

“Words cannot begin to describe the pain I am feeling,” he writes. “I learned this business through the eyes of a father and Christina was like a second daughter to me. All I wanted to do was assist her in achieving her musical dreams while protecting her from the pitfalls associated with the business. I never could have imagined this horrific event being one of the pitfalls needing to be avoided. In Christina’s honor, I have created a GoFundMe page to assist her family in their time of need.”

Teefey signed Grimmie when she was just 14 years old. She and Gomez toured together in 2011 for the latter’s We Own The Night Tour. That Saturday night Gomez gave a heartfelt tribute to Grimme, performing “Nobody” while mouthing the words “I’m sorry” to the audience. The mood was quite emotional, but the singer managed to gather the strength to talk about about “the deranged fan” who murdered her close friend.

“When she was 14, we met her and my parents and I signed her,” Gomez said, her voice quivering as she spoke. “One thing about Christina and her family is that she holds her faith so closely to her. And I think it’s not about a religion and it’s not about anything or good deeds. It’s just that she had faith, and I don’t really understand how this really happened, but I would like to dedicate this next song to her.”

That deranged fan was 27-year-old Kevin James Loibl, a resident at St. Petersburg, Florida who traveled to Orland’s Plaza Live venue. There Loibl fatally shot Grimmie before doing the same to himself at an autograph signing. While Orlando police have successfully identified the murderer, there’s no clear evidence of a motive nor any that the two knew each other.

Help Christina’s family by visiting the official GoFundMe and watch footage of Gomez’s tribute. Be sure to keep Grimmie and her family in your thoughts and prayers.