Here are the pre-burn orbit parameters:
The initial parameters of the geocentric phase are period 2,482 min, apogee 108,498 km, perigee 183 km, and inclination 30.2 deg.
It was already in a highly eccentric orbit. The burn at perigee would have kicked it out of earth orbit and sent it on its way. An explosion, or something came loose inside would be my guess.