Ruben Espinosa

Prosecutor Rodolfo Rios told the Televisa network Thursday that the suspect was one of three men whom surveillance cameras recorded leaving the apartment building.

Rios declined to identify the man, who he said was previously convicted of rape and causing injuries and served nearly 10 years in prison.

Rios also wouldn't say whether the suspect had confessed to either the killings or the robbery police say was apparently carried out at the apartment.

Rodolfo Rios Garza says the person was identified by a fingerprint found in the apartment and that it registered to someone with a criminal record.

Photojournalist Ruben Espinosa was found dead Friday, shot in the head, his body bound and tortured. The attackers also killed his friend, Nadia Vera and two of her roommates, as well as their 40-year-old housekeeper.

Espinosa had fled the state of Veracruz after being threatened and harassed by strangers.

The United National High Commission on Human Rights also condemned the killings, saying the bodies had signs of torture and sexual violence and that the climate of impunity "is one of the obstacles to practicing freedom of expression in Mexico."

"We are all outraged by this crime," Mayor Miguel Angel Mancera said in a news conference. "There will be no impunity in this matter. No line of investigation will be discarded."

But the killings may have had to do more with the four women found dead alongside Ruben Espinosa, 31, who worked for the investigative magazine Proceso and other media, Mexico City prosecutor Rodolfo Rios Garza said in news conference.

Rios did not identify the other victims, only giving their ages as 18, 29, 32 and 40. All were shot in the head with a 9 mm weapon. He said they are focusing on the crime as a feminicide, though they have not discarded other motives.