According to The Huffington Post, Power died in Uganda while on assignment following an explorer who was attempting to walk the length of the Nile. Heatstroke is believed to be the cause of death, and he was only 39-years-old.
I didn't know Matthew, but because I've been a Harper's Magazine subscriber for years, I did know some of his wonderful writing, particularly, "Continental Drift: River vagrants in the age of Wal-Mart" and "The Magic Mountain: Trickle-down economics in a Philippine garbage dump." I read these when they first appeared in the print issue and heartily recommend them both.
Life is short, and for many far shorter than it should be, but it sounds like Matthew Power made the most of his 39 years of living. Here's a nice tribute by Power's friend, V.V. Ganeshananthan, and another by Donovan Hohn.
Carry on, then.