The 28-year-old, named locally as Armin Schmieder, told his fans 'today you fly with me' before his leap, from a mountain top near Kandersteg in Switzerland, ended in tragedy.
Images from a video posted online show the pilot readying his wingsuit before pocketing his phone and taking off.
After a few moments, a shout can be heard and the sound of impact.
The Zurich daily Blick reports that followers watching the video reacted with horror.
Some sent messages asking that he 'write or say something.' But all that could be heard on the video was the sound of cow bells, the newspaper reports. The video couldn't immediately be verified.
Bern cantonal police said the body of a 28-year-old Italian citizen was recovered near Kandersteg, a popular BASE jumping location.
Police spokeswoman Jolanda Egger declined Saturday to confirm the man's identity.
She said the cause of the accident was still being investigated.