VALRICO — A man with a history of arrests on domestic violence charges was shot and killed by his wife Sunday night during a fight at their Lithia Ridge home, the Hillsborough County Sheriff's Office said Monday.

Robert L. Walker, 65, who deputies said was shot "at least once," died at the 3913 Crosstree Lane home. His wife, Cynthia Walker, 56, was released from custody Monday morning after questioning.

After consultation with the Hillsborough State Attorney's Office, sheriff's officials said she was released without charges being filed. The investigation continues, the Sheriff's Office said.

"Cynthia Walker has been fully cooperative with investigators, and evidence at the scene has corroborated her statements," the Sheriff's Office said in a news release. "Detectives also established that Robert Walker had prior arrests for domestic battery against Cynthia Walker."

In 2010, Robert Walker was charged with felony domestic battery by strangulation and obstructing a law enforcement officer without violence, a misdemeanor. Online court records show that the domestic battery charge was later reduced to a misdemeanor.

Both charges were dropped by prosecutors after Walker successfully completed a pretrial intervention program, according to online records.

Walker also was arrested on April 13, 2008, and charged with felony aggravated assault with a deadly weapon and misdemeanor domestic battery, according to online court records. The charges were dropped later that year.

Walker also was charged with misdemeanor spousal battery in 1992. But he was acquitted after a nonjury trial.

Online court and Florida Department of Law Enforcement records do not show the alleged victims in those cases, though Cynthia Walker was listed as a witness in the 1992 case.

Nobody answered the door at the Walker home Monday afternoon. An outside light was still on, and a PT Cruiser automobile with one tire nearly flat sat in the driveway. Cynthia Walker also could not be reached by telephone.

Although the Sheriff's Office said the shooting occurred just before 10 p.m., three neighbors told the Tampa Bay Times that they heard multiple gunshots about 7 p.m.

Dennis Foussat, 62, whose Harrogate Drive home runs along the back of the Walker home, said he heard as many as eight or nine shots, separated into three bursts. Foussat said he was swimming in his pool at the time.

Dana Bader, 65, who lives two houses down from the Walkers on Crosstree, said he, too, heard at least three shots sometime around 7 p.m. "I didn't think anything about it," he said. "I thought it was just kids playing with firecrackers."

Homicide investigators worked through the night conducting interviews and examining physical evidence, deputies said.

Walker's autopsy will be conducted by the Hillsborough County Medical Examiner's Office.

William R. Levesque can be reached at levesque@tampabay.com.