Police Chief Todd Coring said at a press conference on Sunday that Nigel Edge of Oak Island is accused of opening fire from a boat into a crowd gathered at American Fish Company in Southport.
Coring said the location was "targeted" but did not elaborate.
The shooting, which erupted about 9.30pm on Saturday, took place along a popular stretch of bars and restaurants in the historical port town about 48km south of Wilmington.
Investigators said Edge piloted a small boat close to shore, stopped briefly, fired, and then sped away.
Edge is charged with three counts of first-degree murder, five counts of attempted first-degree murder and five counts of assault with a deadly weapon.
He could face additional charges, Coring said.
"We understand this suspect identifies as a combat veteran. He self-identifies. Injured in the line of duty is what he's saying, he suffers from PTSD," Coring said, referring to post-traumatic stress disorder.
Edge is scheduled to make his first court appearance on Monday, District Attorney Jon David said.
He is being held without bond.
Among the five people hospitalised with injuries, at least one "is now clinging for their life," David said.
Roughly half an hour after the shooting, a US Coast Guard crew spotted a person matching the suspect's description pulling a boat from the water at a public ramp on Oak Island.
The person was detained and turned over to Southport police for questioning, officials said.
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