CONCORD, Calif. (AP) _ A botched plot to extort $100,000 from an elderly couple led to the murders of five people, including blues guitarist Elvin Bishop's daughter, who may have been in on the scheme, police said Thursday.

Two brothers and their female roommate were arrested on drug possession and burglary charges, and police consider them ``potential suspects'' in the slayings.

Selina Bishop, 22, may have joined in the scheme before she was killed, Concord Police Lt. Paul Crain said Thursday.

``Obviously she had a relationship with these people. We're trying to understand exactly what her involvement was, and at what point she became a victim,'' Crain said.

Among the biggest mysteries are when and where Bishop was killed. Her remains and those of Ivan and Annette Stineman were believed to be spread among least eight duffel bags pulled from a Sacramento County river this week.

It's also unclear whether the Stinemans were forced to write two checks before they were killed or if someone forged the signature, Crain said.

Bishop _ or someone else posing as her _ called a bank before the checks written to her name were cashed last week, Crain said. One police theory is that she may have fled and was killed after objecting to the Stinemans' deaths.

Fingerprints show Ivan Stineman is one of the three victims whose remains were found in the bags, and coroners were working Thursday to positively identify his wife and Bishop as the others.

A chainsaw and a sawhorse were found inside the Stineman's van, which was abandoned in Oakland with the keys still in the ignition, Crain said.

Bishop had been dating Glenn Helzer, 30, who had been the elderly couple's former stockbroker, police said.

Investigators said that connection helped them link the disappearance of the Stinemans and Bishop last week to the shooting deaths of Bishop's mother, Jennifer Villarin, 45, and her friend Joseph Gamble, 54, who were found in Bishop's apartment.

Glenn and his brother Justin Helzer, 28, were arrested Monday along with their roommate Dawn Godman, 26, in their home down the street from the Stinemans. Police also found drugs in the home.

The three were arraigned Wednesday but did not enter pleas. They were being held without bail and are due back in court Friday.

Public defender Penny Scanlon, who represented the Helzers and Godman at their initial appearance, did not immediately return a phone call Thursday. It was unclear whether private attorneys had been hired for any of them.

While no one has been charged in any of the murders, Glenn Helzer made statements linking himself to the elderly couple's disappearance, Contra Costa Deputy District Attorney Hall Jewett said.

The night Ivan Stineman, 85, and his wife, 78, were last seen alive, a neighbor saw two men with long ponytails entering their home, Crain said.

Bishop was last seen alive with Glenn Helzer three days later at a Berkeley pub. The next morning, her mother was shot to death in Bishop's bed.

As police raided the Helzers' home, Godman and Glenn Helzer fled out the back door. Glenn Helzer allegedly broke into a nearby home, armed himself with two kitchen knives and cut off his ponytail with a pair of scissors.

Had he killed somebody? His hostages wanted to know.

``Not yet,'' Helzer replied, according to police.

The Helzers and Godman were raised as Mormons, and Glenn and Justine had served their two-year missions. Glenn later married and has two daughters. The Helzers' grandfather, Helmuth Helzer, told The San Francisco Chronicle that the two brothers apparently got involved with drugs and that Glenn lost his stock broker job at Dean Witter and abandoned his family.

Bishop reportedly met Glenn Helzer at a ``rave'' concert. Local newspapers reported that she, the Helzers and Godman were active in the ``goth'' movement, dressing in dark colors and spending time in bars frequented by followers of occult activities.

Elvin Bishop, best known for his 1976 pop hit ``Fooled Around and Fell in Love,'' has not commented on the case, according to Mike Grill, who works for Alligator Records in Chicago.

Carma and Jerry Helzer, the suspects' parents, sat through Thursday's news conference at the Concord Police station.

``I know what the truth is, but I will not tell you what the truth is,'' Mrs. Helzer said, adding: ``I would like the victims' families to join me in prayer.''