Concord, N.H. — A man accused of opening fire at a New Hampshire country club in September was indicted on murder, attempted murder and assault charges, authorities said Thursday.

Hunter Nadeau, 24, of Nashua, is accused of killing one person and wounding two others at the Sky Meadow Country Club on Sept. 20 while a wedding reception was going on nearby. Authorities said the indictments made public Thursday show the case is being pursued under multiple theories of murder, as well as attempted murder and assault charges.

Nadeau was originally charged with second-degree murder, but Thursday’s indictments show he has been charged under alternate theories with both first-degree and second-degree murder. Authorities declined to discuss a possible motive for the shooting, and they said they do not believe the victims were targeted by Nadeau.

Police credited restaurant patrons with responding quickly during the chaos, and witnesses said one person struck the gunman with a stool to help subdue him. Charlene DeCesare, whose husband, Robert DeCesare Jr., was killed, said he was shot while protecting her and their daughter.

The gunfire also wounded restaurant manager Steven Burtman and patron Brianna Surette. Authorities declined to provide additional details, and a message was left for Nadeau’s attorney on Thursday.

Court documents described Nadeau as having been charged in April with simple assault after being accused of shoving a manager at a grocery store to the floor. In September, both sides agreed to place the misdemeanor charge on file and dismiss it if Nadeau remained on good behavior.

A chef, Dave Manganello, said he knew Nadeau as a banquet server at the club several years ago. In a September interview, Manganello described him as borderline arrogant but said he did not think Nadeau was capable of violent crime, adding: “He wasn’t like sweet as pie or the nicest guy you ever met.”