Alex Murdaugh was flown to hospital by helicopter after he was grazed by a bullet shot at him as he changed a tyre by the side of a road.
The law firm PMPED, which was founded by Mr Murdaugh’s great-grandfather, said it was hiring an accounting firm to go through its books and see how much money was allegedly missing.
It has not said how much money it believes was stolen from them.
“This is disappointing news for all of us. Rest assured that our firm will deal with this in a straightforward manner. There’s no place in our firm for such behaviour,” the law firm said in a statement.
The law firm’s move came just hours after Mr Murdaugh had announced he had resigned in a statement of his own, and just two days after he himself was shot on a rural road in Hampton County.
“The murders of my wife and son have caused an incredibly difficult time in my life. I have made a lot of decisions that I truly regret,” he said in a statement of his own.
“I’m resigning from my law firm and entering rehab after a long battle that has been exacerbated by these murders.
“I am immensely sorry to everyone I’ve hurt including my family, friends and colleagues. I ask for prayers as I rehabilitate myself and my relationships.”
Police say that Mr Murdaugh was able to call 911 after he was injured in the Saturday afternoon shooting, reportedly carried out by someone driving a pickup truck.
Mr Murdaugh was flown to Memorial Health University Medical Center in Savannah, Georgia, for treatment of a non-life-threatening “superficial” head wound, say officials.
“Alex resigned after being accused of diverting lawyer fees from the firm,” said Mr Murdaugh’s attorney Jim Griffin.
“These allegations prompted him to confront a dependency and he voluntarily checked into an in-patient substance abuse rehab facility after being discharged from the hospital today.”
Investigators are still probing the deaths of Maggie Murdaugh, 52, and Paul Murdaugh, 22, outside the family’s hunting property on 7 June.
Mr Murdaugh says he found the bodies when he returned having been away checking on the health of his own mother and father.
In 2019, Paul Murdaugh was indicted in a boat crash that left a 19-year-old female passenger dead, with a police report stating that the teens were “grossly intoxicated.”
The family reportedly did not co-operate with law enforcement, and Paul Murdaugh, who had been driving the boat, was never given an alcohol breath test.
He later pleaded not guilty to three felony counts of boating under the influence and had been out on a bond of $50,000 when he was killed.