Lindley Johnson, head of the near-Earth object program at NASA headquarters in Washington, D.C., says an asteroid the size of a football field could wipe out a major city.

"This seems like the latest example of BP taking a calculated risk that goes wrong, " says Kimberly Gladman, director of research at GMI, a corporate governance ratings firm.

Tyler Hadley, 17, allegedly killed Blake and Mary-Jo Hadley on Saturday before locking their bodies in a bedroom and inviting guests round.