Update September 27: The Associated Press is reporting that McKinley's funeral will be held this morning in suburban Atlanta. There's a brief AP writeup here.
Update September 22: There's still no concrete "why," but a picture has emerged of a McKinley depressed by his inability to play football due to his knee injuries.
This updated Denver Post article is your best spot to learn more.
First reporting September 21:
In what appears to be an suicide, Denver Broncos wide receiver Kenny McKinley (and former University of South Carolina star) was found dead at his home at approximately 3:25 p.m. on Monday, September 20.
After setting records for the Gamecocks, 2009 was McKinley's first pro season but was hampered by injuries. -- Right now there seems to be general surprise at the 23-year-old's death, with those who are talking about the death saying the boisterous athlete seemed in generally good spirits having just returned from a trip home.
The Denver Post has perhaps the best report, it can be read here.
Also of note: