MEMPHIS  When Monica Bledsoe spoke to her younger brother late last May, he seemed his old upbeat self. He had just led his first sightseeing tour of Little Rock, Ark., for their father’s new tour bus company and all went well. The tips had flowed.

A week later, her brother, Abdulhakim Mujahid Muhammad, opened fire with a semiautomatic rifle on a military recruiting center in Little Rock, killing one soldier and wounding another.

Ms. Bledsoe was stunned. “I would never have thought this could happen,” she said.

Eight months after the shooting, Mr. Muhammad’s family is still sorting through the confusing pieces of his shattered life. A gentle, happy-go-lucky teenager, he had become a deeply observant Muslim in college, shunning gatherings where alcohol was served. He traveled to Yemen to study Arabic, married a Yemeni woman, was imprisoned and then deported for overstaying his visa. After returning to Memphis last year, he stewed with anger about the wars in Iraq and Afghanistan.

Recently, Mr. Muhammad, 24, thrust himself back into the news by claiming in a note to an Arkansas judge that he was a member of Al Qaeda in the Arabian Peninsula, a terrorist group based in Yemen. He asked that he be allowed to plead guilty to capital murder, a request that will probably be denied.