Dear Friend, I was reading translations of Bhasa's mahaabhaarata dramas yesterday. There the story from the original (I presume vyaasa's) is also mentioned. I read therein that due to a boon (vara), it was karNa who slew ghaTotkacha. With the Ekalavya discussion presently going on, I thought this may be interesting. Regards! - J. K. Mohana Rao