Abel Gutierrez, 27, fatally shot his sister, Lucero, in an apparent murder-suicide Thursday in California, police said. Family members told police they suspected he suffered from post-traumatic stress disorder.
Investigators searched during the night for his mother, Martha Gutierrez, 52, but there was no sign of the woman, police said.
Police said they found clues at the family home indicating that she might be hurt.
"It's horrible. We have no idea where she is," Gilroy police Sgt. Chad Gallacinao told The Associated Press. "We are desperately trying to find her."
A roommate called police to the Gutierrez apartment Wednesday night. Arriving officers found the bodies of Gutierrez and his little sister dead from gunshot wounds.
Police said they had contact with Abel Gutierrez as recently as late last month, but did not find that he was a danger to himself or his family.
Family members, however, told the San Jose Mercury News that Gutierrez said that he wanted to kill himself "all the time" and would ask if that would hurt them.
Faustino Gutierrez, 46, Martha Gutierrez's brother, said the young veteran would sit on the sofa twirling a handgun and also brandished a rifle inside the family's apartment. He had recently returned from Iraq.
"He said he killed a lot of people in Iraq," Faustino Gutierrez said. "It was in his conscience, and he didn't want to live anymore."
A niece, Kristell Gutierrez, said she knew her uncle was "very mean" to his mother and blamed her for his father leaving the family.
In one instance, Gutierrez threw a plastic jug of laundry detergent at his mother, and the container broke on the outside stairs, according to Alissa Fernandez, a downstairs neighbor. As his mother and sister cleaned the mess, Gutierrez yelled, "Are you done?"
"She was scared of her son," Fernandez told the Mercury News.
Mario Reyes, a neighbor who lives beneath the Gutierrez family, told KNTV-TV that he thought he heard a scuffle - but no gunshots - around the time police say the shooting occurred.
Gallacinao said officers found at least two firearms used in the killings, but he would not say whether Gutierrez left a suicide note. Police had been called to his apartment on Feb. 29, but Gutierrez did not seem dangerous and did not meet the criteria to be placed on a psychiatric hold, Gallacinao said.
Instead, police began working with the family and Office of Veterans Affairs in Palo Alto to help him.
Gutierrez had been receiving care at a VA facility in Puget Sound, Wash., confirmed Kerrie Childress, a spokeswoman for the Department of Veterans Affairs Care System in Palo Alto. She said she could not provide further details.
Jeri Rowe, public affairs director at the Puget Sound facility, said she was unable to confirm or release any information concerning Gutierrez because of privacy regulations.
