According to investigators, Cruz allegedly killed all six of his relatives – including two children – during a botched robbery attempt.
Ramos, 19, was also charged in the six killings, but police have not specified what role she played in the murders, referring to her only as an “accomplice.”
Police officials told reporters during a press conference held Thursday that DNA evidence recovered from the Feb. 4 crime scene linked Cruz to the murders.
Cellphone records were also used to connect Cruz to the killings.
Detectives tell PEOPLE Cruz and Ramos allegedly confessed taking part in the six slayings.
Three generations of the same family were wiped out during the violent episode.
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During Thursday’s press conference, Chicago Police Superintendent Eddie Johnson characterized Cruz’s actions as “an act of barbarism,” noting he couldn’t recall a more disturbing case coming across his desk during his 28 years with the department.
“For area residents, it was a shocking and sudden loss of friends and neighbors as well as fear for their safety,” he said. “For CPD officers and detectives, it became personal.”
Commander William Dunn told reporters it appears the Martinez family let Cruz into the home because they knew him. An argument between Uribe and one of his aunts precipitated the killings.
Police allege he fatally shot Maria Herminia Martinez, 32, before “systematically” stabbing and beating his other relatives to death.
Detectives found all six victims – Rosaura Martinez, 58; her husband, Noe Martinez Sr., 62; 13-year-old Leonardo Cruz; his brother, Alexis Cruz, 10; and Noe Martinez Jr., 38 – scattered throughout the home.
It was unclear Friday if Cruz or Ramos had lawyers or whether they’d entered pleas to the charges against them.
Information on both suspects’ bail amounts was also unavailable.