As treasurer of a Champlin elementary school Parent Teacher Organization, Melissa O’Brien was responsible for paying the bills. Prosecutors said she did — her own.

O’Brien, 31, and her husband, Dustin O’Brien, 34, of Champlin, have been charged with felony theft by swindle in the disappearance of more than $54,000 from the Oxbow Creek Elementary School PTO.

Hennepin County Attorney Mike Freeman said Thursday the O’Briens may have taken $72,000 or more. He noted that there was $98,000 in the PTO account in October — and that less than three months later, the account was depleted.

“When something like this happens, it’s surprising, it’s shocking, it’s disappointing,” said Oxbow Creek Principal Rolf Carlsen. “So much of what we do is based on trust.”

According to court documents: Melissa O’Brien wrote checks totaling $25,000 payable to herself, her husband and her mother, all drawn from the PTO account. She also withdrew $11,000 in cash from the account, failing to use the money to pay PTO expenses or to pay the PTO’s insurance premium. She set up withdrawals from the account to pay personal bills, totaling approximately $1,100.

Authorities said O’Brien, who has three children at the school, admitted in January that she stole money from the PTO and that she devised several schemes, including writing checks and setting up direct payments to her creditors. A manager of the Champlin branch of the Anoka Hennepin Credit Union said O’Brien cashed three checks from the PTO account, totaling $1,553.58.

O’Brien implicated her husband, telling authorities he also cashed several PTO checks.

The O’Briens are not commenting, said their attorney, Shawn Betts.

Melissa O’Brien volunteered to fill the vacated treasurer’s position in August, said Darla Noah, Oxbow Creek PTO president. She underwent a background check, as do all the PTO board volunteers.

“She worked in the classrooms, in the holiday gift shop every year and with our [fundraising] carnival,” Noah said of O’Brien. “There was no reason to think this would happen.”

When O’Brien took over, the PTO account had $11,800. But fundraising activities at the start of the school year pushed the account’s balance to nearly $100,000.

When a PTO check bounced in early January, Noah realized the unthinkable may have happened.

Yet it happens more often than people fathom, said Linda Rodgers, the Anoka-Hennepin School District’s coordinator of parent involvement. “PTOs are nonprofits and, like many nonprofits, the board members are changing constantly,” Rodgers said. “Leadership turns over. It’s hard to establish a strong tradition of tight management.”

Freeman, whose staff has prosecuted many nonprofit embezzlement cases, said that having two signatures on checks of more than $500 can alleviate problems — as can regularly scheduled treasurer’s reports presented by someone who doesn’t sign the checks.

The O’Briens made an initial appearance in Hennepin County District Court on Wednesday. The county attorney’s office is asking for restitution if the O’Briens are convicted and that they serve six to nine months in jail, Freeman said.