Updated

Police arrested a 20-year-old man on murder charges Wednesday as they investigate the slayings of two teenagers, each shot in the head, whose bodies were found behind a grocery store in an Atlanta suburb.

Jeffrey A. Hazelwood is accused of killing Natalie Henderson and Carter Davis early Monday morning in a case that left parents in Atlanta's sprawling northern suburbs on edge, Roswell Police Chief Rusty Grant said at a Wednesday news conference at Roswell police headquarters.

While investigators are unsure of the motive, "we believe he acted alone," the chief said.

Hazelwood was being held at the Roswell Detention Center on two counts of murder, and was expected to be transferred to the Fulton County Jail later, police said.

A delivery driver spotted the bodies behind a Publix store, Det. Zachary Frommer said. The Fulton County medical examiner said each teen was killed by a bullet to the head.

Officers located Hazelwood at a gas station not far from the crime scene, and brought him to police headquarters for questioning around 5 a.m. Wednesday, Grant said. He's been "generally cooperative" during the interviews with detectives, Frommer said.

Hazelwood is from Roswell, and also has ties to the Woodstock and east Cobb County areas, Frommer said. He had been staying with family and friends at various places in the Roswell area in the recent past, the detective said.

Though police declined to specify exactly what led them to pursue Hazelwood as a suspect, it was a combination of physical evidence, electronic evidence, interviews and old-school police works that resulted in the arrest, Frommer said.

"It just seemed like everything came together," Frommer said. "This was a true, old-fashioned type of police case."

The two 17-year-olds were about to start their senior years at high school. Henderson attended Roswell High, just across the street from the Publix, and Davis was a standout lacrosse player at River Ridge in nearby Cherokee County.

Davis also played lacrosse in Rapid City, South Dakota, before returning to finish high school in Georgia, where he had lived as a child, Black Hills Lacrosse Association past president Richard Sudmeier said.

"Our players up here in Rapid City, we called him 'Georgia.' That was his nickname," Sudmeier said in a telephone interview with The Associated Press on Wednesday.

Davis wore No. 6 when he played on the Black Hills Lacrosse team, so Sudmeier said teammates may wear helmet stickers with the number in his honor.

The South Dakota players plan to gather Friday to remember Davis, who was always willing to help his former teammates improve and "was pretty much like a second coach," said Zach Hockert, the varsity coach at Black Hills Lacrosse.

"If I could have a whole team of Carter Davises, we'd be unbeatable," Hockert said Wednesday.