William Devin Howell, a drifter with a lengthy criminal record, was working odd jobs around central Connecticut in the summer of 2003 when several people, some of them women with histories of substance abuse, began to vanish.

Howell was convicted in the death of one woman in 2005, but the other cases remained unsolved, despite suspicions raised by sex tapes and blood found in the van he used for a landscaping business.

Since the discovery, announced this week, that a total of seven victims were buried in woods behind a strip mall in the city of New Britain, Howell has emerged as the prime suspect in a case that could make him of the most prolific serial killers in New England history. He is serving a 15-year prison sentence for manslaughter, but nobody has been charged in the other six deaths.

At a news conference Wednesday, police revealed that one of the seven sets of remains belonged to Nilsa Arizmendi, the woman Howell was convicted of killing after she was last seen in Wethersfield, Connecticut.

"I can't even imagine how many people didn't get hurt because Mr. Howell was convicted of manslaughter in 2005," Wethersfield Police Chief James Cetran said.

A lawyer who represented Howell in the past has declined to comment, and it is not clear whether he currently has legal representation.

Howell, 45, grew up in Hampton, Virginia, where he was in and out of jail in his early 20s for crimes that were often related to drugs. By the time the 5-foot-9, 220-pound man with a tattoo on one biceps arrived in Connecticut, his record included criminal convictions for larceny and burglary in Virginia, as well as arrests in Georgia and New Jersey.

A nephew in Virginia said that Howell came to live with his family in the early 1990s, but that his mother kicked him out after a few weeks because Howell could not stay out of trouble. Howell had burned bridges with family members before moving north from Virginia, but he continued to write to family while incarcerated and received prison visits from at least one relative, the nephew said. The nephew spoke on condition of anonymity because he did not want his name publicly associated with the case.

The slaying that led to his capture began as a missing-person case.

Arizmendi, a 33-year-old mother of four, was last seen with Howell in July 2003 at a grocery store parking lot in the 1985 Ford Econoline van that had a sign saying "Quality Lawn Service. Call Devin" and listed his phone number. Arizmendi and her boyfriend, Angel Sanchez, had previously smoked crack cocaine with Howell at a motel, and she had gone to see him to buy drugs, according to the arrest warrant affidavit.

Wethersfield police went to interview Howell at his girlfriend's house in November 2003, but they did not have a warrant, and Howell headed south soon thereafter. The van was recovered in North Carolina in 2004, and by then Howell was wanted in Connecticut for an alleged assault on his girlfriend, Dorothy Holcomb, and was also a suspect in Arizmendi's disappearance.

Tests on blood found in the van showed a match with Arizmendi, and Howell entered an Alford plea to manslaughter in the middle of a trial for her slaying, acknowledging that prosecutors had evidence to convict him. Investigators also found in the van six videotapes of Howell having sex with women and blood from an unknown second person, and authorities asked the public for any information that could help identify the person.

As Howell was awaiting trial, a fellow inmate said Howell told him that the Arizmendi case was circumstantial and that "the state didn't have a body and he didn't want the body to show up because it would do him in." He also told the inmate he hated prostitutes, according to court records. Howell was later convicted of intimidating a witness for threatening to kill the inmate, Thomas Rodrigues, because he shared the information with investigators.

A hunter in 2007 came across the partial skeletons of three female victims, and the remains of four others — two women, one man, and one that has not yet been identified — last month were found buried in the same area in the latest of several searches. Drug use has been a common thread among most of the victims, according to police and court documents.

Police have not said how the seven people were killed or how they concluded that a single person was responsible for all the slayings.