Police dash cam,video recently released.Little Rock,Ark. LITTLE ROCK, Ark.City and state police have closed their investigations into last summer's shooting of Arkansas' Democratic Party chairman without offering an explanation of why the attack occurred.

Bill Gwatney died Aug. 13 after being shot three times by a man who had been fired from his job at a Target store that morning. The shooter, Timothy Dale Johnson, was chased into Grant County, where he was shot and killed after threatening officers.

A 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 police spokesman.

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 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.

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. Gwatney owned three General Motors car dealerships and was a state senator for 10 years before becoming the state's Democratic chairman last year.

A separate report released Thursday by Arkansas State Police found that the officers who fatally shot Johnson acted properly. Prosecutor Eddy Easley said no criminal charges would be filed in connection with Johnson's death.

When officers stopped Johnson in Grant County - after a 30-mile chase from Little Rock - they ordered him to get down, the report said. Instead he pulled from his vehicle a rifle case that he tried to open even as officers shot him.

Weapons in Johnson's possession when he was stopped included the Ruger .357 Magnum used to kill Gwatney, the report said.

According to the report, Johnson's sister, Janice Peacock, told troopers that Johnson had begun taking classes at Arkansas State University at Beebe and asked her to help him pay for his tuition. She said that her brother had also pawned some of the firearms from his gun collection to help pay for tuition.

Peacock said her brother was "always interested in politics, but never to the point of threatening to kill anyone," the report said.

"I really thought he would commit suicide," Peacock told investigators. "I never thought he would hurt anybody."