Getty / Backgrid Composite

Paul Stanley 's back out in the world after the death of his longtime friend and bandmate, Ace Frehley ... running errands in Beverly Hills days after his passing.

The singer-songwriter stepped out on Saturday, holding a FedEx package under his arm while wearing a button-down black shirt and a pair of faded blue jeans. Backgrid

Stanley kept a pretty neutral expression as he went about his errands ... though he expressed heartfelt condolences earlier this week at the passing KISS' former guitarist.

As you know ... Frehley passed away Thursday after his family made the difficult decision to take him off life support . Gallery Launch Gallery Getty

Ace suffered a nasty fall in his studio back in September which caused a brain bleed ... and,

See Full Page