By AP/KWMU
Springfield, Ill. – 
Police in Springfield, Ill. arrested a man Tuesday morning they think shot and killed an unarmed guard at the State Capitol Building on Monday.
They say 24-year old Derek Potts was the man who walked into the Capitol and shot Bill Wozniak once in the chest.
Wozniak later died. He was married and had two teenage kids.
Potts was arrested about 7:15 a.m. in Springfield, officer Carlos Sours said. Sours said he didn't have any details about the arrest but that police would have a statement later.
Police have said they don't know of a motive for the shooting. "We have no idea why he came here and did this," Col. Larry Schmidt, chief deputy director of the Secretary of State's police force, said Monday.
Potts is originally from Olney in downstate Illinois but now lives in Springfield.
Wozniak, who had worked at the Capitol for 18 years, died in a hospital operating room shortly after the 1:38 p.m. shooting.
Illinois State Rep. Rich Brauer (R-Petersburg) had known Wozniak for about 30 years. He said Wozniak had a wife and two teenage children and had moved to the small community of Petersburg decades ago to escape the violence of Detroit.
"What can you say? He was just real friendly and outgoing," Brauer said. "To me it's incredible that we have this guy that is in charge of security at the Capitol, and he's there with no protection at all. And a guy comes in with a gun."
To hear a report from Illinois Public Radio's Bill Wheelhouse about the questions over security that were raised by Monday's shooting, click on the 'listen' icon above.