The man suspected of killing at least seven people and burying their bodies behind a New Britain shopping center has been identified as William Devin Howell, a 45-year-old currently incarcerated at a Connecticut prison on separate manslaughter charges, multiple sources familiar with the investigation tell NBC Connecticut exclusively.

Howell’s current 15-year sentence at the Garner Correctional Institution stems from the homicide of Nilsa Arizmendi, a 33-year-old Wethersfield resident who disappeared in 2003.

Arizmendi's sister reported her missing on July 31, 2003 and told police she had not seen Nilsa since July 24, according to court documents.

On Aug. 14, 2003, Nilsa's boyfriend also reported her missing and said the last time he saw her was on July 25, when she got into "Devin's" blue van on the Berlin Turnpike to get drugs, court documents state. Her body was never recovered.

He was taken into custody in North Carolina in 2004 and his then-girlfriend's van – which Arizmendi was last seen entering – was seized as evidence.

When police searched the vehicle, the cushion on the back seat was gone. In its place were three sofa cushions.

The remaining back cushion was stained with blood, according to police, and authorities discovered Arizmendi’s blood in the van, along with the blood of an unidentified person.

Police also found a videotape with footage that shows two other women, according to the DCJ. Their identities – and their fates – are unknown.

Howell was charged with murder on May 16, 2005 and went to trial, but pleaded guilty to the lesser charge of manslaughter in a deal with prosecutors in 2007, according to the state Division of Criminal Justice website.

In September 2006, he was accused of threatening to kill a cellmate who he claimed "snitched" on him, according to an arrest warrant application.

Howell was working odd jobs in Connecticut when Arizmendi disappeared – cutting grass in Wethersfield, Hartford, New Britain and West Hartford.

New Britain police said on Monday that investigators have now recovered the bodies of at least seven people from a swampy, wooded area behind the shopping plaza at 593 Hartford Road, where a hunter found the first set of remains in 2007.

Police have declined to name the suspected killer, citing an ongoing investigation, but said the person they are looking at is no longer a threat to the community. The office of the chief state's attorney also said they have a suspect, but are not identifying who it is.

Four of the seven victims found behind the shopping center have been identified – all as women who vanished in 2003. The first three sets of remains, found in 2007, belong to Diane Cusack, 55, Mary Jane Menard, 40, and Joyvaline Martinez, 24.

Police said on Monday a fourth set uncovered late last month has been identified as Seymour resident Melanie Camilini, who was 29 years old when she disappeared. Monday would have been her 42nd birthday.

Authorities did not directly answer the question on Monday when asked whether the victims were linked by anything other than the person who killed them.

A medical examiner is working to identify the other newly discovered skeletal remains.

Police Chief James Wardwell said during the news conference on Monday that the remains had apparently been buried for at least a decade.