I just heard on Al Jazeera that the Fajr 5 rockets were originally designed by the Chinese and redesigned by Iran. Then they were supplied to Hezbollah and then found their way to Hamas.
Hamas claimed that they no longer had any Fajr 5 rockets left not too long ago, and yet surprisingly they are still firing them... Sounds like they may have come across a new supply...

As the Mythbusters would say.... Revolutionary Guard overseeing missile fire...? Plausible.