Calgary police have laid charges against a couple who investigators believe are the grandfather and step-grandmother of a five-year-old boy who died last summer after suffering several blunt force trauma injuries to his head.

Allan Edgardo Perdomo Lopez and Carolina Del Carmen Perdomo were arrested and charged with manslaughter on Friday morning after a year-long investigation into the boy’s 2015 death, which was deemed a homicide last month.

The child, Eneas Emilio Perdomo, died last July after he was taken to Alberta Children’s Hospital with injuries that family members said came from a series of accidents, police said.

Hospital staff later noticed swelling and bruising all over the boy’s body that didn’t seem to match typical activity for a five-year-old boy, police said.

Eneas died a week after being admitted to hospital. An autopsy later determined that he died from multiple blunt force trauma injuries to the head, police said.

In a press conference on Friday, Calgary police explained why it took 12 months for investigators to lay charges.

“We received our last medical report on this file on June 30, 2016 -- so a few short weeks ago. That’s how long it takes. We have radiologists, emergency doctors, forensic pathologists, neuropathologists all weighing in on this,” explained CPS Acting Staff Sgt. Michael Cavilla.

“The medical evidence is monstrous, as you can well imagine. That is what takes the time.”

The five-year-old boy moved to Calgary from Mexico City, where his mother lives, in February 2015 to live with his grandparents in pursuit of “a better life,” Cavilla said.

After Eneas’ death, Calgary police travelled to Mexico to meet with the boy’s mother, who is the daughter of Allan Perdomo Lopez, as part of their investigation.

Three other young people, including two teenagers and a young woman in her 20s, lived with the couple at a home in southeast Calgary. Cavilla said that police are assured “they are in a safe spot.”

He said police could not confirm any details about any alleged ongoing abuse against the boy.

“I can’t speculate on whether or not it was ongoing or one incident … this matter is before the courts, I can’t get in to that,” Cavilla said.

The investigation into the child’s death remains ongoing, Cavilla said, and he asked anyone with information to reach out to police.

Lopez and Perdomo are scheduled to appear in a Calgary court on Monday.

With a report from CTV Calgary