Adult-film actor Seth Peterson‘s family is devastated following his sudden and mysterious death this week, forcing his mother to get on a plane to find answers about what happened in the days before he died.

Tiffany Aguirre tells TMZ … her 28-year-old son, real name Adam Aguirre, had been staying alone at a short-term rental home in Portland, OR, and last Saturday, she says Adam’s partner called to tell her Adam had not been responding to phone calls in the past few days.

That prompted Tiffany to call Portland PD to request a welfare check.

Cops tell us they responded to Adam’s place and discovered the body of a deceased male. Police wouldn’t confirm the individual’s identity, but Adam’s mother tells us it was him.

We’re also told his death is not being investigated as a homicide.

Still, Tiffany has a lot of questions … she flew to Portland this week, and now fears her son suffered an accidental drug overdose.

She says she visited Adam’s rental home and found concerning drug paraphernalia.