SPOTSYLVANIA, Va. -- Law enforcement officials say a 15-year-old boy has been charged with second degree murder after he shot and killed a man who was attacking his mom, reports CBS affiliate WTVR.

Sheriff's deputies found the man dead while responding to a call on Tuesday afternoon, according to the station. The man, identified as 37-year-old John Conroy Jr., was the mom's boyfriend, investigators said.

A spokesman told WTVR that earlier that day, Conroy and his 36-year-old girlfriend got into an argument that lasted for hours. Then, the man allegedly began physically attacking her while her son watched.

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"At that point, the 15-year-old son went to a place in the home where he knew there was a firearm," Capt. Jeff Pearce said. "[He] took a semiautomatic firearm...and fired several shots at Conroy."

The teenager's mother was later treated for non-life threatening injuries, according to the station.

Pearce explained that under Virginia law, all homicides are considered second-degree murder. So, detectives, working with the Spotsylvania Commonwealth Attorney's Office, filed petitions for the arrest of the teenager, according to the station.

He wouldn't go into details about the relationship between the teen and Conroy or if the couple had previous problems.

Police say the investigation is still ongoing, but once the investigation is concluded, Commonwealth's Attorney could decide whether to raise, lessen or dismissing the charge altogether, Pearce added.