Late one night when I was younger and still living at home, I had been talking on the phone with my girlfriend while laying on the family couch, getting hornier by the minute. After the phone call, and before I headed off to bed for the night, I listened up the hallway toward my parents bedroom and was sure that they were sound asleep.
Satisfied that they were still asleep (around 1am), I went back into the living room, undressed, lay back on the couch, and started masturbating thinking about the resent call with my girlfriend. My eyes were closed until I heard a floorboard at the open door behind me creak lightly, but was too close to stop what I was doing.
There was a wall mirror beside the front door of the house that I was facing, and in it I could clearly see my mother standing in the shadow of the doorway wearing her usual nightgown for sleeping. However this time, I could clearly see that she had one hand squeezing her left breast while pinching her nipple, and her right hand up inside her nightgown masturbating as well, watching me intently.
After seeing this, I could no longer hold back and shot stream after stream of cum up my chest and into my hand stroking my cock. I stayed that way until it looked as if she had cum as well. She eventually slipped out of the doorway and back to her bedroom as quietly as she could.
When I heard her bedroom door close, I cleaned myself up, grabbed my discarded clothing, turned off the lights, and quickly made it to my own bedroom. I expected something to be said the next day, but to my surprise the incident was never brought up and remained our secret, til this day. It did however lead me into becoming more of an exhibitionist over the years, to see what I could do, and pretend that I wasn’t aware of being seen.