Actually there is one thing in computers that can explode and do a very considerable amount of damage, Capacitors. However, one that could do what has been described would have to be on the order of an entire Farad, which would hold an amazingly high amount of charge (1 coulomb/volt to be exact - a lightening strike carries 3-5 coulombs or charge typically to put that in perspective) and be about as large as a 5 gallon paint bucket. SO, we can probably rule out capacitors as the source....just my 2 cents (and some of what being an electrical engineering student has taught me so far).
My guess would be that it was a CRT that blew and "charred" him. The gasses that come out would be considerably pressurized and can be amazingly hot while not burning themselves, they could badly damage a person (example - steam burns). It is entirely possible that the reporter made the common (noob) mistake of calling the monitor the computer. Definately interested to hear a little more about this.
And for the people saying that there was a bomb in the copmuter, while an entertaining thought, not likely. As it would need to be a focused directional blast like a claymore in order to do what was described without leveling the house, Also he was charred, not "fragged" (I couldnt resist)