The Iraq War veteran who killed his 11-year-old sister and then turned the gun on himself, also shot his mother in his green Mustang, based on evidence found in the car, Gilroy police reported Friday.

By noon, Martha Gutierrez, 52, had not been found. While the investigation is ongoing, police said it is likely her son, 27-year-old Abel Gutierrez shot her sometime after 8:30 p.m. Tuesday, when she was last seen, and left her for dead.

Sgt. Chad Gallacinao said he was still hoping that she still may be alive and urged anyone with information to call police.

Police said the son’s 2000 Ford Mustang, recovered at the family’s home on Kern Avenue, had signs of a “violent assault,” and that a gun had been fired in it. Martha Gutierrez’s cell phone was found in the car.

“She has not showed up to work,” said Grant Cornia, Martha Gutierrez’s supervisor at the Headstart Nursery in Gilroy, where she had worked for at least a decade in the greenhouses. The last day he saw her was Tuesday. “This is definitely a shock to everyone. It’s hit a lot of people really hard.”

On Wednesday, at 9 p.m., police rushed to the family’s apartment complex after a roommate thought something might be wrong; they had told the department earlier that they thought Abel Gutierrez, an award-winning National Guard infantryman, had been suffering from Post Traumatic Stress Disorder since his return from Iraq two years ago.

Inside, they found his sister, Lucero Luna, a middle school student, dead with gunshot wounds to the head. Her older brother was dead nearby of a self-inflicted gunshot.

Abel Gutierrez’s family had been concerned he had been suffering from PTSD upon his return from Iraq, and had even called police in late February to help because of his erratic behavior.

PTSD is an extreme form of anxiety that often makes it difficult for soldiers who have experienced combat to resume normal lives.

Gutierrez had most recently served with the Washington National Guard and living in Tacoma. Guard spokesman Capt. Kevin Kosik said Gutierrez was deployed overseas during Operation Iraqi Freedom in 2009 and came back in spring 2010. He had joined the Guard on Dec. 20, 2008, and served with A Company, 1st Battalion/161st Infantry Regiment, where he was an infantryman, or foot soldier.

Kosik said he won several awards: the Iraq Campaign Medal, the Army Commendation Medal, the Global War on Terrorism Medal and the Combat Infantryman Badge.

Before that, Kosik said Gutierrez had been on active duty with the Army based in Fort Lewis, Wash., where he had been a specialist.

“The Washington National Guard community has been following the heartbreaking news out of Gilroy, California involving one of our citizen-soldiers,” a Guard statement read. “We are struggling to come to grips with the tragic events that have unfolded, and we extend our deepest condolences to the friends and family of those who were lost.”

Kosik deferred all other questions to Gilroy police.

When police met with Gutierrez on Feb. 29, officers decided not to take him into psychiatric custody but referred him for help at Veterans Affairs.

Gallacinao said that a 15-year police veteran, who also is a military veteran, went to the family’s house and did not think Gutierrez was a danger to himself or to his family; both criteria needed to take someone away to be evaluated at the hospital.

“At the end, the family said that they did not fear him, and they just wanted him to get help,” Gallacinao said. “The officer went above and beyond in referring him to Veteran Affairs.”

A VA spokeswomen in Puget Sound, Jeri Row, confirmed Gutierrez sought treatment in Washington state and in Palo Alto, both for a “brief amount of time” but did not elaborate.

In the weeks leading up to the violence, neighbors and relatives at the complex reported that Abel Gutierrez was known there for his often troubling, frightening and aberrant behavior toward family and strangers.

After Gutierrez returned from Iraq, relatives and neighbors at his apartment complex described the former soldier as openly troubled. They said he often used profanity at people, threatened them and generally seemed on the edge of some kind of violent outburst.

Faustino Gutierrez, 46, Martha Gutierrez’s brother, said the young veteran would sit on the sofa twirling a handgun and also displaying a rifle inside the family’s apartment.

“He said he killed a lot of people in Iraq,” said Faustino Gutierrez. “It was in his conscience, and he didn’t want to live anymore.”

Contact Lisa Fernandez at 408-920-5002. Follow her at Twitter.com/ljfernandez.