Several cans and prescription pills were reportedly found in the 34-year-old star's bedroom and bathroom when police discovered his body at his Lancaster home on Saturday.
Cops believe Aaron's dead body had been in the tub for some time, with sources telling TMZ there was a smell of decomposition and the water had turned an unnatural color.
Aaron's body was discovered by his housekeeper on Saturday morning. She allegedly went to ask him if he wanted coffee and entered his bedroom after hearing his dogs going wild. She found Aaron in the bathtub and dialed 911.
Sadly, law enforcement showed up at Aaron's home hours before his death to do a welfare check. According to police sources, cops arrived at the singer's residence on Friday around 2 AM.
They were met by his housekeeper and forced to leave after Aaron caught wind of the situation. He reportedly screamed for his housekeeper to not let the responding officers in and ordered them to leave.
Aaron's housekeeper did not see him after the welfare check on Friday until she discovered his body.
The I Want Candy singer struggled for years with drug abuse; however, his cause of death won't be revealed until the Los Angeles County Coroner's Office gets the toxicology results.
No suicide note was reportedly found at the scene, and there were no signs of foul play.
Aaron's estranged brother, Backstreet Boy singer Nick Carter, broke his silence following the tragic news of his death.
"My heart has been broken today," Nick wrote on Instagram Sunday. "Even though my brother and I have had a complicated relationship, my love for him has never ever faded," he captioned a series of childhood photos of the duo.
"I have always held onto the hope, that he would somehow, someday want to walk a healthy path and eventually find the help that he so desperately needed," he continued. "Sometimes we want to blame someone or something for a loss. But the truth is that addiction and mental illness is the real villain here."
Over the weekend, Nick broke down in tears during a tribute to his late brother during the Backstreet Boys tour, leaving his bandmates to console him.
Aaron left behind an 11-month-old son, Prince, whom he shares with his ex-girlfriend, Melanie Martin.
If you or anyone you know is struggling with addiction issues, help is available. American Addiction Centers offers help for those struggling with addiction. You can call their support line at 866-244-1070.