The "Self Care" rapper, real name Malcolm James McCormick, was found unresponsive at his San Fernando Valley, California home, and was pronounced dead at the scene by authorities. He was 26.
Early reports suggested Miller had died from a suspected drug overdose, and tributes quickly poured in from his friends, fans, and hip-hop peers after the news hit headlines.
And on Saturday, Ariana shared a silent salute on Instagram with a black-and-white snap of her ex sitting on the grass, looking up at the camera.
The image marked Ariana's first public response to his passing, and came hours after she disabled the ability for followers to comment on her posts, having been inundated with hurtful messages from his upset fans.
The couple had dated for two years until parting ways in May, shortly before Miller was arrested for driving under the influence (DUI) and hit and run in Los Angeles.
At the time, the "No Tears Left to Cry" hitmaker faced a backlash from his devotees, who appeared to blame Ariana for Mac's downfall as she had already moved on to a new relationship with comedian Pete Davidson, to whom she is now engaged.
The pop star hit back and insisted no one should ever be forced to stay in a "toxic relationship", revealing she had tried to help him beat his substance abuse issues.
"I have cared for him and tried to support his sobriety & prayed for his balance for years (and always will of course) but shaming/blaming women for a man's inability to keep his s**t together is a very major problem...," she responded. "I will continue to pray from the bottom of my heart that he figures it all out and that any other woman in this position does as well."
According to The Blast, Miller's autopsy was completed by the L.A. County Medical Examiner on Saturday, but the official cause of death was listed as "deferred", pending further tests.
Sources claim there was no "obvious" evidence of drug use at the scene, but toxicology tests have been ordered to determine if substance abuse played a part in his passing.
Funeral arrangements have yet to be announced, but Miller's loved ones have since released a statement about the tragedy.
"He was a bright light in this world for his family, friends and fans," the statement read. "Thank you for your prayers."