Wild dogs have mauled and killed four people whose bodies were found over the past two weeks in a park on the edge of Mexico City, authorities say.
In one case, a teenage girl frantically called her sister on her phone to plead for help from the attack as it took place; tragically, it was too little, too late.
Neighbours of the Cerro de la Estrella, a partly wooded, hilltop park surrounded by the city's poor and populous Iztapalapa district, first found the bodies.
A 26-year-old woman and a 1-year-old child in the area were discovered on December 29, authorities in Mexico's sprawling capital city said.
The woman, Shunashi Mendoza, was missing her left arm, and prosecutors said that both she and the boy had bled to death and been partially eaten.
Then Friday, visitors to the same park found the bodies of a teenage couple - Alejandra Ruiz, 15, and boyfriend Samuel Martinez, 16 - who bled to death.
"Experts have established that due to the gravity of the wounds, at least 10 dogs were involved in each attack," Mexico City prosecutors said.
In the second attack, they had gone to the park Friday afternoon.
The girl called her sister Diana at around 7 p.m. pleading for help.
"Several dogs are attacking us, help me!" the girl screamed.
The call then stopped.
Ruiz told Milenio Television she thought her sister was joking and still doesn't believe her sister was hurt or killed by the wild dogs despite the call.
"What kind of dog can tear the skin from your whole arm and leave just bone and if it was an attack dog why didn't it attack her neck?" Ruiz asked.
"What's most shocking is that one of her breasts was mutilated."
She said she later visited the place of the attack and saw no pools of blood. "There needs to be a thorough investigation," she added of the tragedy.
Antemio Maya, president of the Street Dog Protection association in Mexico City, also doubts that dogs could have killed the people found in the park.
"It's not the behavior of street dogs to kill humans," Maya said.
Maya said authorities should focus on sterilizing pets and educating people about pet ownership instead of spreading the idea of killer animals.