Don't panic, this is not uncommon at all, and nothing to worry about.
Proteins in the urine occasionally crystalise within the urethra, which can cause the 'split spray' scenario. It usually happens when you visit your future in-laws' house and they have just had light pink carpet carpet tiles in the bathroom!
Seriously this crystalisation is perfectly normal, and the urine will flush the crystals through the next time, or time after he urinates - to be sure, tell him to have a 'sit down' and use his fingers to point the flow right into the bowl before he starts. Once 'normal service' is resumed, it may happen again, but as i say, it is not serious at all, nothing to wrry about.