You can't just have a quaint little gun buyback event anymore. Someone has to ruin all the fun with a live hand grenade. The New Gospel Temple Church of God in Christ (all one name) in the Bronx was hosting the buyback yesterday where local residents were invited to turn in their firearms for $200 bank cards, no questions asked. But apparently around 1:30 p.m., there was a question that had to be asked to one —specifically, "is that a hand grenade?" That was then followed by "can someone call the Bomb Squad?" and then finally "would everyone please exit the building as quickly as possible?" After carting out the "improvised hand grenade," the NYPD held the man responsible, whom the Daily News calls "a dimwit," but it doesn't appear he'll be charged with anything. There was no indication as to whether he will receive payment for the explosive. Just Friday night, Bryant Park was closed for an hour when a man was attempting to sell another (?) grenade.