User blog comment:FairyRaven/Fairy Tail Chapter 328: Zodiac, Review and Commentary/@comment-5851664-20130419133538/@comment-7418318-20130419140008

He probably tried to kill her because he was afraid she might prevent the opening of the gate, or close it before any dragons come through.

As for magic near the gate, maybe the "magic sucking" effect was part of the chargeing and ended once the gate was either fully charged, or started to open.