FEDERAL WAY, Wash. -- Police said the mysterious death of a Federal Way woman five months ago is a mystery no more.

Investigators said her husband planned her death using his expertise as an exterminator to poison her.

On November 28, Joe Naimo called paramedics to his home claiming his wife was unconscious and unresponsive. She died that night.

A preliminary investigation and autopsy on 53-year-old Ann Naimo resulted in nothing suspicious, said Cathy Schrock of the Federal Way Police Department. It wasn’t until January, when her blood tests came back and showed lethal levels of the poison, strychnine, were present.

When questioned by investigators, Naimo told several different stories about his wife's death and even admitted at one point that he felt guilty that she had died.

After a five month investigation, Naimo was arrested Thursday and charged with poisoning his wife. Neighbors were shocked to hear of Naimo's arrest.

“That is so scary, we did not know. He told us she had a heart attack,” said neighbor Anna Trann.

At a bail hearing in King County Superior Court, the 62-year-old Joe Naimo was ordered held on $5 million bond.

Naimo is the general manager of AAA Pest Control in Kent. According to a probable cause affidavit, his job has provided him with extensive experience in the use of poisons. Prosecutors said Naimo is allowed to purchase and use commercial rodenticides and would be knowledgeable about the poison strychnine.

When asked about the charges against his father, Nicholas Naimo said, “It's bull**** that's what I think.”

Nicholas didn’t want to talk as police searched the family home for evidence.

Neighbors said the Naimo family was quiet and they never suspected the man living next door could be charged with murder.

Charging documents did not mention a possible motive in this case.

Joe Naimo remains in the King County Jail and he is expected to be arraigned on charges of first-degree murder sometime next week.