A father branded as 'pure evil' has finally been convicted for murdering his five infant children more than 30 years after he committed the horrific crimes. 

Paul Perez, 63, was convicted in Woodland, California, a city outside of Sacramento, on Tuesday for multiple counts of murder and deadly assault on a child under eight for the gruesome killings of his five infants.

District Attorney Jeff Reisig said: 'These crimes involved pure evil. The defendant should die in prison. May the souls of his murdered children rest in peace.'

The announcement marks the end of a decades-long fight for justice for the five babies born between 1992 and 2001. 

Authorities called Perez a 'transient' and weren't alerted to the deaths of his children until an infant's body was found in 2007.

It wasn't until 2019 that advancements in DNA technology identified the child as Nikko Lee Perez, according to the Yolo County Sheriff's Office. 

The grim discovery came when a fisherman named Brian Roller was using a bow and arrow to catch fish and accidentally struck a box. 

Roller opened it to find decomposing remains of a three-month-old baby boy. Authorities believed the infant had been in the box for at least six months before the discovery. 

Paul Perez, 63, seen in court in 2020, was convicted this week for the murder of his five kids 

Authorities arrested Perez in 2020, 13 years after one of the infants' remains were found in a cooler in a California pond 

Little Kato was killed by his father shortly after he was born in 2001 

The infant was wrapped in a Winnie the Pooh Blanket and a layer of plastic. Authorities described the 'box' the infant was placed in as a metal cooler, weighed down with other objects. 

'When I opened that box, I was 99 percent sure it was a human body but I wanted to hold on to the belief that maybe it wasn't,' Roller told the Associated Press in 2020. 

'When I saw one of the officers start to cry, I knew right then that what I was thinking was true.'

The discovery led to a chilling investigation into the infant's identity. Advanced DNA testing finally identified him as Nikko Lee Perez. 

The California Bureau of Forensic Services discovered that he was born on November 8, 1996, in Fresno, and connected the child to Perez. 

Investigators learned Nikko had four siblings. Two of the children were named Kato, and another infant was also named Nikko.

The fifth sibling was identified as Mika. The children were born in Fresno and Merced, California, and were all believed to have been killed within months of birth. 

Perez was arrested and charged with the murder of his five children, with a special circumstance of torture, in 2020.