Prosecutors announced a fourth arrest Monday in the case of an illegal immigrant charged with killing three people in Missouri after being released from a New Jersey jail.

Nyadia Burden, 25, purchased the bullets that Luis Rodrigo Perez, 23, used in two separate shootings Nov. 1 and Nov. 2 that left three people dead and two wounded, Missouri prosecutors said.

Burden was charged with murder as have Perez and an alleged accomplice Aaron Anderson, 19. Perez's New Jersey girlfriend was charged with tampering with evidence. They were all arrested a few days after the shootings.

Burden told police that Perez said he was going to kill Josh Hampton, 23, one of the victims, KYTV reported.

ILLEGAL IMMIGRANT KILLED 3 AFTER 'SANCTUARY' RELEASE FROM CUSTODY, ICE SAYS

She said after purchasing the bullets, she, Perez and the accomplice went back to her house where they marked the bullets with a sharpie as they were quoting a song called “Murder on My Mind,” according to the station.

She told police that on Nov. 1, Perez, Anderson and Sabrina Starr left her house and returned later around midnight, the station reported. She remembers Perez saying Hampton was dead and he and Anderson saying that the others were shot because they were there.

Luis Rodrigo Perez (Associated Press)

She also told police she didn't go because she was pregnant, according to the station.

Perez was being held at the Middlesex County Jail when ICE Enforcement and Removal Operations placed a detainer on him that was ignored.

ICE officials said Middlesex County’s sanctuary policy was to blame.

"This case is, unfortunately, a tragedy that happened that may have been avoided," John Tsoukaris, the field office director for ICE Enforcement and Removal Operations in Newark told mycentraljersey.com last week. "The only county jail right now in the state that refuses to work with us is the Middlesex County Jail."

Middlesex County has defended its policy.