SACRAMENTO COUNTY (CBS13) — A man accused of shooting and killing a homeless woman has been linked to another shooting involving a homeless person.

The accused gunman, 28-year-old Christopher Michael Franklin, is said to be a veteran of the armed forces and is not homeless.

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Sacramento County Sheriff’s deputies are trying to find a motive for why Franklin allegedly walked up to a homeless woman in October and shot her in the head near his well-kept south Sacramento County home.

Deputies say it isn’t the first time Franklin had targeted a homeless person. He’s been linked to the shooting of another transient in the area. That man survived.

Neighbors say Franklin, who they identified from a Facebook picture, displayed odd behavior, but they had heard the veteran was having a hard time adjusting after returning from active duty.

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Family members did not open the door at the home on Monday.

Neighbors say it wasn’t long ago that the home was surrounded by deputies who seemed concerned about his welfare.

Psychologist Andrew Mendonsa works with patients suffering from post-traumatic stress disorder and says while the condition doesn’t excuse criminal behavior in most cases, it could explain some of it.

“Combat veterans, and combat personnel have experiences traumatic incidences and somethings there’s like no coming back to reality when they get home,” he said. “It can run the gamut of anything from someone being delusional to just far detached from reality.”

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It’s not known if Franklin has been diagnosed with PTSD, but Mendonsa says many go undiagnosed, refusing to admit they need help.