Bill Gwatney died Aug. 13 after being shot three times by a Searcy man who had been fired from his job at a Target store that morning. Timothy Dale Johnson was chased into Grant County, where he was shot and killed after threatening officers.
A city police report said Johnson was on an antidepressant and that the drug may have played a part in his "irrational and violent behavior."
Autopsy results said Gwatney died from a shot to the head. Johnson was shot six times.
"I wish there was a conclusion, but there wasn't," said Lt. Terry Hastings, a spokesman for the Little Rock Police Department.
Authorities discovered a note with a telephone number and the word "Gwatney" on it in Johnson's home, but the report found that it was a telephone number for Gwatney Towing Company in Jacksonville, which is no longer in business. The note also listed other numbers for local towing companies, the report said.
The FBI also reviewed the history on Johnson's computer, and found that he visited Wikipedia, Yahoo and news sites the day before the shooting. Johnson also visited the Web site of the Bureau of Alcohol, Tobacco and Firearms that day, the report said.
Gwatney owned three General Motors car dealerships and was a state senator for 10 years before becoming the state's Democratic chairman last year.
The 986-page report says police searched through electronic and paper files at Gwatney's businesses for Johnson's name, but that it never turned up.
"There's really no answer as to why he did it," Hastings said.