A 16-year-old high school student charged with shooting a teenager at the Rockville Metro station Friday told detectives he was angry because the victim had threatened to rob him the day before, according to arrest records made public Monday.

Kevin Nguyen met with several friends Thursday night to “develop a plan of retaliation,” according to court papers. On Friday afternoon, he and some friends went to the Metro station to find the other 16-year-old.

“I heard you wanted to rob me,” Nguyen said, after approaching the boy in a pedestrian tunnel just outside the station’s turnstiles.

“Yeah, what are you going to do about it?” the other teenager responded, according to Nguyen’s account to police.

The suspect, 5-foot-4-inches tall and 110 pounds, started shooting with a semiautomatic pistol and kept firing as the victim tried to run away, according to arrest records. Hit by as many as five rounds, the victim collapsed in the tunnel with wounds to his leg, abdomen and groin, according to court papers. He survived his wounds.

Police cordoned off a section of the Rockville Metro station after the shooting Friday. (Dan Morse/Dan Morse)

As Nguyen fired, police said, one round struck an 18-year-old bystander. She was treated for her wound.

“This sort of conduct does not get any more egregious,” Assistant State’s Attorney Peter Feeney said in court Monday during the first hearing in the case.

The midday shooting at Rockville’s Metro station erupted on an otherwise calm, sunny Friday as early commuters were arriving home from work. A short escalator ride takes passengers from an elevated platform toward turnstiles, which lead to a wide pedestrian tunnel. People can head east, toward a parking lot, or west, toward downtown Rockville.

Nguyen was charged as an adult with attempted murder, along with 17-year-old Tavares Harris, who police say gave Nguyen the gun. Both boys attend Richard Montgomery High School in Rockville, one of the top schools in the county, officials said.

Both suspects, as well as the victim, are members of gangs, Feeney said in court. He did not say what, if any, role that played in the shooting.

Reached Monday night, the victim’s mother said her son is recovering from his wounds. “He’s still in a lot of pain, but it’s not as serious,” she said.

She said her son goes to school regularly, is working to get his grades up and is not a member of a gang. She said he never intended to rob or hurt Nguyen. “This kid came after my child,” she said.

Montgomery District Court Judge William G. Simmons ordered Harris held without bail. Nguyen’s bail review was delayed until Tuesday, when his attorneys — Paul Kemp and Thomas DeGonia — said they will ask that he be transferred to a facility for juveniles because of his age and “diminutive size.”

Kemp said Nguyen’s family immigrated from Vietnam in the 1970s. “They’re citizens; they’re very hard-working people,” he said.

About an hour after the shooting, a person or persons threw at least three rocks through windows at the Nguyen home, Kemp said.

Barry Helfand, an attorney for Harris, said he had not been able to discuss the case with his client. He said that Harris’s mother told him that her son goes to church with her twice a week, is a good student and always goes to school. “In view of these allegations and her statements to us, it’s a mystery,” Helfand said.

Bad blood appears to have been brewing between the teenagers since at least Thursday, after school was let out, according to arrest records.

Several teenagers became involved in an “altercation,” during which Nguyen heard a 16-year-old say he intended to rob him, according to arrest records. The two groups then went their way.

Later that night, Nguyen, Harris and several other teenagers met to develop the retaliation plan, court papers say. “I am going to kill him,” Nguyen said, one of the teenagers would later tell detectives.

At some point Friday, Harris called Nguyen. The two met, and Harris told Nguyen he had a gun in his bag, according to police. Police said in court papers that it was not clear where Harris got the loaded weapon.

The pair, joined by others, went to the Metro station looking for the other teenager — coming in through the west side of the tunnel and spotting their target with his friends at the other side. Nguyen grew angry and told Harris: “Give me the gun, give me the gun. I am going to shoot him,” according to arrest records.

Nguyen later told detectives he hadn’t known that he hit a bystander. He fled out the western exit toward Rockville’s Town Center area, dropping the gun into a trash can on the way, according to police. Within eight minutes, officers apprehended him near a Shell gasoline station.

Police staked out the King Farm area, where Harris was known to hang out, and took him into custody without incident, according to court papers. Police found the gun in the trash after Nguyen told them where it was, officials said.