Lector ain't dead, think a little
Minerva was smiling and saying "good" after Sting supposedly killed Genma with the lightbeam through his chest, i know that girl had plans for the guild and she somehow wanted to take out Genma. She's like former Ultear who work behind the scenes to further her plans using every dirty trick in the book and in this case right before Genma's attack hit she used her power to teleport Lector out of there last second making it seem like he was killed when vanishing.
This is what she used against Lucy
And don't forget she blocked Natsus hit on Genma while suddently appearing to hold Happy as hostage to stop Natsu's raging.
Use your heads, everyone was shocked including Rufus and Orga, Minerva wasn't meaning she had a hand in it and that cunning chick wouldn't leave things to chance. She made a small interference to set up a scene. If that's not enough for you guys, tell me untill now. Has Hiro had the balls to kill off anyone in his story, anyone good? No.
I think she will also have this to drive Sting's actions, i bet the 5th day when everyone's gonna fight Sting will go crazy and beat the shit out of Natsu, he'll have almost no chance, i think he will possibly take out Natsu and for some reason Minerva would want that, to eliminate the threat that is Natsu for her own agenda. Sting will have the power of his feelings against Natsu in this fight, the shitty excuse Natsu had as a source of strength when beating Sting & Rogue in Dragon force last time. Also, the 5th day will be when Rogue will have a chance to fight Gajeel one-on-one like he wanted to.
That's my theory and knowing Hiro, it has like a 90% chance of coming true.