via NBC Los Angeles
Apparently the autopsy was only recently completed because cause of death is hard to determine from only a head and limbs; the rest of the body has yet to be found.
It was not previously reported that Campos-Martinez was the prime suspect, but of course significant others always are. Nothing unusual there. It was also not reported, however, that the body parts were found the day after Campos-Martinez finally filed a missing person report, prompted by a visit from the police to the apartment the two men had been sharing for some six months.
Detectives were investigating an anonymous tip that friends had been unable to contact Medellin. Medellin had supposedly been on a trip to Mexico, though the aforementioned prosecutor is now suggesting that the 66-year-old retired airline employee made no such trip.
via LA Times
According to a prosecutor, the two men met through a third party and the suggested motive was an impending breakup.
Campos-Martinez is currently being held in Texas, pending extradition back to Los Angeles.