A woman was charged Thursday with killing her husband, whose body was hacked up, placed in three suitcases and dumped in the ocean last year.

Prosecutor Patricia Prezioso said Melanie McGuire (search) was having an affair at the time of the slaying. McGuire's lawyer, Michael Pappa, said they were shocked by her arrest, though they had known for months she was a suspect.

McGuire, 32, pleaded not guilty to first-degree murder. Bail was set at $750,000.

Authorities said they believe that she shot William McGuire (search), 39, in the couple's Woodbridge apartment in April 2004 and likely had help dismembering his body and transporting the suitcases to Virginia.

"There are more people involved in this matter" and more arrests are expected, state Attorney General Peter Harvey said at a news conference. He declined to elaborate.

Melanie McGuire bought the pistol used to shoot her husband from a Pennsylvania gun shop two days before the slaying, Harvey said. Black trash bags found in the McGuires' apartment were linked to trash bags containing the severed body parts and a paint chip found on one of the bags was fingernail polish, Harvey said.

During the investigation, McGuire told detectives in Virginia Beach that she and her husband had a violent argument after closing on a $500,000 home and that he had stormed out. His car was later found abandoned at a motel in Atlantic City.

Melanie McGuire filed for divorce three weeks later, without ever having reported her husband missing. In the divorce papers, she accused him of slapping her and excessive gambling and drinking.

The suitcases were found around the same time near the Chesapeake Bay Bridge-Tunnel in Norfolk, Va.

Harvey said authorities found no evidence that McGuire was a battered woman or that her husband had a gambling problem.

William McGuire was an adjunct professor and a senior programmer analyst at the New Jersey Institute of Technology (search), the school said. Melanie McGuire is a nurse.

"I am just so stunned," William McGuire's sister, Nancy Taylor, said Thursday from her home in Florida. "It doesn't bring him back, but at least justice will be served."