Two good possibilities are:

1) Your friend didn't change his bongwater. As someone else noted above, bongwater is, well, very nasty. Warm water with decaying biomatter is an excellent way to encourage bacterial growth. Change the water often. The more often, the better.

2) If the ice wasn't from an ice bag in a grocery store, the ice itself may have been unsafe. Most tapwater will be safe, unless it's from a well and isn't properly filtered. More importantly, those ice cube trays you make ice cubes with can grow mold and bacteria, especially if you use something other than water in them (making ice cubes from juice or coffee, for instance). If you don't wash ice trays regularly, they can get pretty gross. If your friend's ice cube trays were dirty, this may be the problem.