Man Pleads Guilty to Killing His Doctor Ex-Girlfriend, Mom, 6-Month-Old Daughter and 2 Other Children

A California man accused of killing five people — including his 6-month-old baby daughter — in 2015 has pleaded guilty to their grisly murders. He also has been sentenced in the death of his ex-girlfriend’s son, who died a year prior to the murders.

On Tuesday, Martin Martinez was sentenced to five consecutive life terms in prison without the possibility of parole for the murders of his mother Ana Brown-Romero; his niece Esmeralda Navarro; his ex-girlfriend Dr. Amanda Crews; and her two children, Elizabeth Ripley and 6-month-old Rachel Martinez, whom they shared, according to the Office of the District Attorney Stanislaus County.

Chief Deputy District Attorney Annette Rees said the prosecution had initially sought the death penalty for the murders, but Martinez’s defense attorneys recently approached her office with a proposed resolution.

Martinez’s attorney did not immediately respond to PEOPLE’s request for comment.

As part of his plea, the 35-year-old admitted to killing the two women and three children inside a Modesto, Calif., home on July 18, 2015.

Martinez entered the residence through the garage door before stabbing his 57-year-old mother Brown-Romero to death with a knife, according to the Office of the District Attorney Stanislaus County. He then suffocated Elizabeth, his ex-girlfriend’s 6-year-old daughter from another relationship, and his 5-year-old niece Esmeralda when he found them upstairs in the master bedroom, prosecutors said.

According to Rees’ office, Martinez then went on to suffocate baby Rachel in a downstairs bedroom.

Prosecutors said Martinez waited by the front door following the four murders and stabbed Crews to death when she entered the house.

Crews, a physician with the Stanislaus County Health System, was attending a conference that morning and had stopped to buy batteries for her garage door opener before returning home, according to The Modesto Bee.

“We know the door was locked so we know she turned to lock the door and that’s when he set upon her,” Rees said. “We believe he had a key because the door was locked when the victims were discovered.”

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“That is the way he let himself in and then he locked it, after stepping over his mother in the laundry room, and left that way.”

In his court appearance on Tuesday, Martinez was also convicted of voluntary manslaughter in the death of Christopher Ripley, Crews’ 2-year-old son who died on Sept. 30, 2014 of blunt force trauma to the head.

At the time of Christopher’s death, Crews told authorities that Martinez was a 50 percent caregiver of her children, according to a search warrant affidavit obtained by PEOPLE. According to the report, daycare staff had reported three suspicious injuries to Christopher around the time he was potty training. Crews denied that Martinez caused the injuries but “did agree that two of the injuries were at home when Martin Martinez was present.”

Martinez was reportedly babysitting Christopher when he received his fatal injury in 2014. His story about how the boy was injured changed several times, the report stated.

A pathologist later concluded that Christopher’s death was “consistent with Christopher’s head hitting the tile floor as a result of abuse.”

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According to the Office of the District Attorney Stanislaus County, Martinez is set to face court on March 12 to hear family members provide victim impact statements.

Previously, a family friend described Crews to PEOPLE as a doctor who “loved her career and was good at it.”

“She was solid and real. She listened with all of her heart and she didn’t tell you lies,” Dr. Mary Harris told PEOPLE in 2015. “She had a laugh that would light the world on fire. If she was laughing near you, you would have to join in. You couldn’t be close to the laugh and not share it.”

If you suspect child abuse, call the Childhelp National Child Abuse Hotline at 1-800-4-A-Child or 1-800-422-4453, or go to http://www.childhelp.org. All calls are toll-free and confidential. The hotline is available 24/7 in more than 170 languages.