“i adored you from the day i met you when i was nineteen and i always will,” she wrote on Instagram, alongside a throwback black-and-white video of the pair laughing together.
“i can’t believe you aren’t here anymore,” she added in the emotional post. “I really can’t wrap my head around it. We talked about this. so many times. i’m so mad, i’m so sad i don’t know what to do.”
Continuing, she wrote, “you were my dearest friend. for so long. above anything else. i’m so sorry i couldn’t fix or take your pain away. i really wanted to. the kindest, sweetest soul with demons he never deserved. i hope you’re okay now. Rest.”
In the video, Miller appeared to start telling a story to Grande before the pair broke out into laughter together.
“Makes me so happy,” Grande can be heard telling Miller off-camera.
“I’ll tell you the story as many times as you want,” he sweetly added.
Shortly after sharing the heartbreaking tribute to Miller, the “God Is a Woman” singer, 25, also went on to post a photograph of a dreary grey sky on her Instagram Story.
This is Grande’s first Instagram post since last week, when she honored Miller one day after his death by posting a black-and-white photo of the rapper without a caption.
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Miller was pronounced dead at 11:51 a.m. at his Studio City, California, home, the Los Angeles County Department of Medical Examiner-Coroner confirmed in a statement to PEOPLE.
A cause of death is yet to be determined, but a source previously told PEOPLE the rapper had gone into cardiac arrest after appearing to suffer a drug overdose.
Earlier this week, Frankie Grande, 35, also posted an emotional tribute to the late rapper, sharing that he felt “beyond heartbroken over Malcolm’s death.”
“He was a good friend and was wonderful to my sister,” Frankie, who like Miller has struggled with substance abuse, continued, before adding that the late rapper encouraged him to get sober.
On Tuesday, an insider told PEOPLE Grande is “distraught” following her ex-boyfriend’s death.
“She completely broke down after she found out about Mac,” the insider said at the time. “She can’t believe he isn’t here anymore. He was such a special person to her. She is very, very sad. … This is a nightmare for her.”
Grande and Miller — who collaborated on tracks “The Way” and “My Favorite Part”— took their romance public in September 2016; they split in late April after dating for two years.
She is expected to attend his funeral, scheduled for later this week in Pittsburgh.
If you or someone you know is in need of help, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.