Police released this image of one of the suitcases they say contained remains. (Credit: Delray Beach Police Department)

(CNN) -- A Florida man has been charged with first-degree murder on suspicion of killing and dismembering his wife, whose remains were found in suitcases on a beach last month, authorities said Thursday.

William Lowe, who was arrested Wednesday, is accused of killing his 80-year-old wife, Aydil Barbosa Fontes, Delray Beach Police Detective Mike Liberta said Thursday at a news conference.

Investigators allege Lowe, 78, fatally shot Fontes in the head, dismembered his body in his Delray Beach apartment and placed the remains in suitcases and a tote bag before disposing of them at his local beach, Liberta said. Authorities believe Fontes was killed sometime between July 17 and July 20, police previously said.

During his first court appearance Thursday, Lowe pleaded not guilty to first-degree murder and abuse of a corpse, online court records show.

Marc Shiner, an attorney representing Lowe, told CNN in an email Thursday that Lowe is a "former Marine who honorably served our country." Shiner added that the defendant "hopes that the whole truth will come out in the courtroom."

Lowe was being held without bail Thursday at the Palm Beach County Jail.

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The defendant was seen several times at the location where the remains were found, the affidavit says.

The investigation began July 21, when police received calls from people who reported seeing suitcases they thought contained human remains in or near the Intracoastal Waterway in Delray Beach, about 15 miles north of Boca Raton, Florida, according to a probable cause affidavit.

The clues led detectives to three suitcases filled with human body parts that day. Police first found a suitcase floating in the water and, shortly after, found two more suitcases in nearby locations along the beach, police said.

A tote-like bag with more remains was found during a canal search the next day, the affidavit says.

Police released this image of one of the suitcases they say contained remains. (Credit: Delray Beach Police Department)

(Credit: Delray Beach Police Department)

"This is probably the worst thing I've ever seen," Liberta said.

Video surveillance of the area where the bags were found and witness statements helped police locate the defendant, Liberta said.

Witnesses told police they saw an older white man apparently look at one of the suitcases, and a witness said the man was there five or six times over a three-day period before authorities found the remains, according to the affidavit.

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Witnesses also told police about a vehicle they had seen a man with the same description enter near where a suitcase was thrown the same day police found it, according to the affidavit. A detective reported seeing a similar vehicle in the area and the vehicle's license plate revealed it belonged to Lowe, according to the affidavit.

When questioned, Lowe told police Monday that his wife had been in Brazil for "about three weeks," according to the document.

Police searched Lowe's apartment and saw large amounts of blood in several areas of the home. Police believe a chainsaw was used in the dismemberment, Liberta said.

"Detectives observed blood splatters throughout the residence, including the living room, dining room, hallway, two bathrooms and master bedroom. Blood was detected in the shower drain of the master bathroom, as well as in the bathtub of the second bathroom," the affidavit says.

Police also saw marks in the living room, hallway and master bathroom along with numerous cleaning supplies, the affidavit states.

Investigators don't know a motive for the killing, Liberta said.

-- CNN's Michelle Watson contributed to this report.