From reading the underlying article, this seems to be highly speculative. There is only that one observation, and no one alse at the time has seen it. It should have been visible to the naked eye over a reasonably large swath of land, although not in Europe and the US where records would most likely be best. Still, someone should have seen it.
Also, its mass is reported as "billions of tons", that's still only a hundredths of Shoemaker-Levi 9 that crashed into Jupiter not too long ago, and only a millionth of Halley's comet. But the impact would still have been significant and bad for humankind, but probably not lethal for the species.
And there is little worry that we may have another close encounter with it. Although its orbital parameters, if it exixts, are unknown, the chances that when it returns on its assumed elliptical orbit to intersect the path of the earth around the sun gets as close again are infinitesimally small. And even taking that shot will have to wait some time, as comets have long orbital periods - think hundreds or thousands of years. And since it was reported as already broken up, chances are that the fragments will dissipate more during the coming millennia.