A woman and her boyfriend are charged with murder nearly two years after a brutal attack in Long Beach.

The incident happened in December 2016, when police say Theresa Kiel was struck repeatedly with a barbell, leaving her in a vegetative state. The Malverne School District teacher succumbed to her injuries on Saturday night.

Only Ralph Keppler, a former New York City correction officer, was initially facing charges. But police now say they believe Francesca Kiel was also involved as well.

"She co-conspired with her boyfriend to kill her mother," said Nassau Police Detective Lt. Stephen Fitzpatrick.

MORE: Couple arrested in fatal 2016 attack on Long Beach woman

Theresa Kiel's attorney says he's also shocked by the case.

"I've been involved in a lot of big cases -- but this was the worst I've ever seen," says attorney Thomas Liotti.

The charges for Keppler were originally attempted murder and assault. Since the victim's death, the charges have been upgraded to second-degree murder for both Keppler and Francesca Kiel.

Police believe the motive was money. The Kiel and Keppler families were in business together, attempting to create a new dating app. Keppler was suing Theresa Kiel, claiming she scammed him out of $350,000 in investment money. Keppler's attorney, Marc Gann, insists his client was set up.

Geoffrey Prime, Francesca Kiel's attorney, denies her involvement.

At the arraignment Monday, the judge ruled that both Keppler and Francesca Kiel will be kept in custody until their next court date on Thursday.