Explain the events upto double fertilization after the pollen tube enters one of the synergids in an ovule of an angiosperm

After entering one of the synergids, the pollen tube releases the two male gamates into the cytoplasm of the synergids.One of the male gametes moves towards the egg cell and fuses with its nucleus. This process is called 'syngamy'. It forms the zygote(2n). The other male gamete moves towards the two polar nucleii located in the central cell and fuses with them to produce a triploid primary endosperm nucleus(PEN). It is known as 'triple fusion'. Since two types of fusion takes place in an embryosac it is called 'double fertilisation'.