Nichols could appear in court as soon as Monday
Ashley Smith said Brian Nichols took her hostage in the parking lot outside her apartment.
Ashley Smith details her experience as a hostage.
A woman's 911 call led to Nichols' capture.
Friends and family of the suspect react to allegations.
ATLANTA, Georgia (CNN) -- Suspected Atlanta courthouse killer Brian Nichols, who is expected to appear in court as soon as Monday, is "defiant" and "kind of proud of his activities," Fulton County District Attorney Paul Howard said.
Nichols, 33, is being held at the Atlanta Federal Penitentiary three days after police said he shot and killed a judge, a deputy sheriff, a court reporter and later a federal customs agent.
When asked if Nichols had confessed to police, Howard replied, "according to the officers that I talked to, he seemed to be rather defiant -- almost kind of proud of his activities."
Saturday morning, Nichols surrendered to police at Ashley Smith's suburban apartment.
Smith, 26, said Nichols held her hostage for hours -- until she eventually gained his confidence, saying, "He said he thought I was an angel sent from God." (Transcript)
Law enforcement officials have said Nichols will face federal and state charges.
Howard said his office plans to "technically resolve" charges in a pending rape case that Nichols was being retried for at the time of his escape. Charges related to Nichols' escape will result "in a very large indictment," he said.
"We plan to charge him with the murders of the four Fulton County residents," Howard said. "We plan to charge him with a number of aggravated assaults, carjackings."
Howard would not say whether prosecutors would seek the death penalty for Nichols.
His answer to that question was, "My gut tells me that this is one of the most gut-wrenching crimes that has ever taken place in our country, and so maybe one can interpret from that."
A Monday court appearance was possible for Nichols, but it could be Tuesday before Nichols faces a judge, a recorded phone message at the U.S. Attorney's Office said.
Following his escape and the killings of Fulton County Superior Court Judge Rowland W. Barnes, court reporter Julie Ann Brandau and sheriff's deputy Sgt. Hoyt Teasley on Friday morning, authorities launched a massive manhunt for Nichols.
He carjacked several vehicles -- injuring a local newspaper reporter -- and then boarded a MARTA subway train north to Atlanta's Buckhead neighborhood, police said.
Authorities said Nichols then shot and killed U.S. Immigration and Customs Enforcement agent David Wilhelm at his home which was under construction near the MARTA station.
He then, police said, stole Wilhelm's truck and drove it to an apartment complex to the northeast in Gwinnett County, where he took Smith hostage.
After 2 a.m. Saturday, Nichols forced his way into the apartment, tied her up and threatened her life, Smith said.
"I basically just talked to him and tried to gain his trust," said Smith, who was widowed four years ago and had lived in the apartment for only two days. (Full story)
Smith said she asked Nichols why he chose her and that apartment complex.
"He said he thought I was an angel sent from God," she said.
Smith said Nichols allowed her to leave to visit her daughter and that she dialed 911 about 9:50 a.m., law enforcement sources said.
As Smith was leaving, she said Nichols asked her: "'Is there anything I can do while you're gone, like hang your curtains or something?'"
"He just wanted some normalness to his life," she said.
Federal and state charges
U.S. Attorney David Nahmias said his office and the Bureau of Alcohol, Tobacco, Firearms and Explosives had filed a federal criminal complaint against Nichols, charging him with possession of a firearm by a person under indictment.
"This is essentially a holding charge that will ensure Mr. Nichols' detention while we sort out additional federal and state charges," Nahmias said.
Deputy sheriff Cynthia Ann Hall -- who police said Nichols overpowered and wounded on Friday during his escape -- was in critical condition Saturday at an Atlanta hospital and is expected to survive.