I found some links on Darkel:In French...and in English
On that second site, press CTRL+F and search for Darkel, and you'll find this:
Another mission source is a street urchin named Darkel (according to Game Informer, he will be replacing the Kill Frenzies that were in GTA and GTA2). Darkel is a rather odd addition who asks you to commit various random acts of violence. One such act mentioned in the IGN preview is to steal an ice cream truck, load it with dynamite, and then set off the bomb after attracting a large enough crowd.
When you take a look
at the man himself, you gotta regret he eventually didn't appear in the game, he'd sure make it even gloomier than it was.