COLUMBIA, S.C. — A peach farmer. A woman and her elderly mother. A furniture store owner and his teenage daughter.

South Carolina serial killer Patrick Burris' seemingly random choice of victims is a major obstacle for authorities trying to determine his motive, according to a former FBI profiler.

The reason behind the six-day killing spree might have died with Burris, 41, a career criminal who was shot to death Monday by police investigating a burglary complaint at a home in Gastonia, N.C. Ballistics from a gun found with Burris linked him to five slayings that terrorized the rural South Carolina community of Gaffney, S.C., 30 miles away.

"This guy has got victims ranging from 15 to 83, he's got males, he's got females," said Mark Safarik, who retired in 2007 as a senior profiler in the FBI's famed Behavioral Analysis Unit. "I don't think that he had the motivation of a serial killer. ... How he got access to them and what the engagement was with these victims would go a long way to tell you what this dynamic is."

Burris was well known to authorities as a bully and was so intimidating a scared elderly man once refused to testify against him and extortion charges were thrown out.

He had repeated run-ins with police for stealing and writing bad checks, and authorities said Tuesday they weren't surprised his crimes escalated. They said Burris, paroled in April after serving eight years in a North Carolina prison, should have never been released.

"He always had a violent streak," Rockingham County Sheriff Sam Page said. "He was very intimidating and very threatening from his appearance: He was at least 6-5 and 250 pounds. You didn't want to mess with him."

Police were still piecing together details of his life. Records show he had lived in Rockingham County, N.C., a rural county near the Virginia border, since the late 1980s, but he also spent a lot of time behind bars. He was arrested more than 30 times in North Carolina alone — the first time in 1989 for blackmail. He also had convictions in Florida, Virginia, West Virginia and Maryland.

Most of his convictions in North Carolina involved stealing from homes and businesses and bad checks, records show.