updated 02/12/2012 AT 1:00 PM ET
•originally published 02/12/2012 AT 1:25 PM ET
It was 9:30 a.m. last Wednesday at the Beverly Hilton and Whitney Houston appeared “out of it,” a source tells PEOPLE.
“She seemed like she was on something,” says the source.
Three days later, after several episodes of reportedly erratic and bizarre behavior, Houston would be dead in her hotel room at age 48, just hours before she was to appear at music mogul Clive Davis’s annual pre-Grammy party.
Coming off another round of rehab last May, she appeared poised for a glittering comeback – she stars in this summer’s film Sparkle – and a triumphant return to the music industry’s biggest week, the six-time Grammy winner serving as mentor to young divas.
But after checking into the Hilton, her odd behavior on Wednesday morning was just the start.