Promissory Payback

Promissory Payback is a FICTION - ADULT: Mystery, Detective, Suspense & Thriller written by Laurel Dewey.
Jane, a police detective is called to the scene of a murder. Carolyn Handel, a 62 year old woman was murdered in her bed. Her hands were tied behind her back and her mouth and nose were covered with duct tape. They found shredded paper stuffed in her mouth.
Her friend, Laura had found her body that morning when she had arrived at Carolyn's home.
The security system appeared to be working and there was no sign of forced entry. A chair was turned so that some one could sit in the chair and watch the woman in bed.
Laura said that Carolyn was running a investment scheme  with 3 other people and these people were wanting their money.
Jane called Carolyn's nephew Joe , the only surviving relative to inform him of her death. Joe said he had been out of town working. He takes pledges to help people in need. Jane asked if he had invested with Carolyn and he said no. He said he had invested once with her and made a lot of money.
When Jane watched the security tapes she found that the security system had been shut off and Laura had turned it on when she came in thinking she had shut it off instead. She also saw Joe coming to Carolyn's door with a bouquet of flowers.
 Read the book to see who had commited the murder and why.