Police and neighbors are struggling to explain why a man described as a loner drove more than 50 km to Arkansas' Democratic Party headquarters and fatally shot its chairman hours after getting fired from his job.

Police said Timothy Dale Johnson, 50, of Searcy, barged into Bill Gwatney's office on Wednesday and shot him several times. There were no signs that Gwatney and Johnson, who was later shot dead by officers, knew each other.

A Target retail store in Conway had fired Johnson early Wednesday because he had written graffiti on a wall, police said. Before noon, Johnson was in Gwatney's office in Little Rock with a handgun.