Law enforcement sources tell us tWitch's note, left at the scene of his suicide, was an ambiguous reference to his past challenges. It's unclear exactly what he was referring to in the note.

We're told investigators have determined tWitch took an Uber from his home to the motel less than a mile from his home Monday morning, and switched his phone to airplane mode so no one could reach or track him.

TMZ broke the story, his wife, Allison Holker, was frantic when she showed up at an LAPD location Tuesday -- saying tWitch left home without notice and wasn't answering her calls.

As we first reported ... it was a motel staffer who discovered the popular DJ and TV host Tuesday inside his room, dead from a self-inflicted gunshot wound.

In addressing her husband's death, Allison said, "Stephen lit up every room he stepped into. He valued family, friends and community above all else and leading with love and light was everything to him."

She continued, "He was the backbone of our family, the best husband and father, and an inspiration to his fans. To say he left a legacy would be an understatement, and his positive impact will continue to be felt. I am certain there won’t be a day that goes by that we won’t honor his memory."