While NASA has not released an official statement regarding the four so-called blood moons of 2014-2015, it has published a report that explains when and why they show up in the night sky. The series of lunar eclipses began on April 15, 2014.
On April 15, 2014, the full moon passed through the Earth's shadow, producing a total eclipse that was visible across most of North America. This began what NASA calls a tetrad, a series of four total eclipses that occur roughly six months apart. NASA expects the final eclipse in the tetrad to take place on September 28, 2015.