One suspect was in custody, and at least three others were being sought last night, police said.
"There were bullets flying everywhere," said Latea Bell, 15, a freshman at the school who witnessed the shooting.
Carlos Bailey, 18, a senior, said, "I was ducking and getting out of the way. Everybody was just running back into the building. It was just chaos. People using their cell phones and screaming."
The victims were identified by friends and relatives as Marcus McLain, a junior star quarterback on the school's football team; William Thomas, a senior football player; Alexander Brown, 17, a basketball player; and Andre Mellerson, an upperclassman.
Three were flown to Maryland Shock Trauma Center by helicopter, and McLain was taken to Sinai Hospital.
Thomas was shot several times, at least once in the neck, and was apparently the most seriously injured. He was listed in critical condition last night.
"It seems like a nightmare for me. I pray for my children every day to be home and to be happy," said his aunt, Ann R. Godwin of Pikesville, while in the hospital waiting area.
Mellerson was listed in serious condition, and Brown was treated and released from Shock Trauma.
A condition for McLain, who was being treated for a gunshot wound to an ankle, was not released.
"We're absolutely praying for the victims. These are fine students, good kids," said County Executive James T. Smith Jr., who arrived at the school as police were still interviewing witnesses. "Everything is being done to apprehend those who were responsible for these heinous acts."
Witnesses said about 100 students were in the parking lot of the Baltimore County school after the game, a charity fund-raiser organized by Del. Robert A. Zirkin of Owings Mills.
A fistfight erupted about 4:30 p.m., and witnesses reported hearing two bursts of gunfire. School had been dismissed at 2:05 p.m.
Michael Thompson, a crisis intervention specialist at the school, heard gunshots and ran outside to find a faculty member praying over one of the victims who was lying on the ground.
Thompson sat another victim on the hood of a car and told him to "just hold on, it'll be all right."
Mellerson stumbled into the school, where Principal Thomas Evans found him bleeding from gunshot wounds to both shoulders. Evans said he tore the youth's shirt off and comforted him until paramedics arrived.
McLain limped into the school through another door and, initially, some faculty members worried that the shooters were inside the building.
The Randallstown varsity baseball team was playing a home game on their field, about 300 yards from the parking lot.
"We told all the kids to get down on the field," said Mike Gelman, the school's athletic director, who called 911.
Randallstown is a middle-class suburb northwest of Baltimore. The high school, with 1,500 students, is on Offutt Road, a long residential street with brick ranch-style homes lining either side.
The basketball game is an annual college scholarship fund-raiser organized by Zirkin. Each year, Zirkin gives out 10 scholarships worth $500 each to Randallstown High seniors who plan to attend an in-state college or university.
Zirkin said he, County Councilman John A. Olszewski Sr. of Dundalk and other current and former politicians and staffers from around the state played a team of faculty members from the school.
Police and witnesses said the shooting apparently did not stem from anything related to the game. "The speculation is that it was a neighborhood argument," said county police spokesman Bill Toohey.
According to Toohey, a car with four men pulled into the parking lot just before 4:30 p.m. The driver, a heavyset man, got out of the vehicle and begin shooting a semiautomatic handgun into the crowd.
He got back into the car and handed the gun to the front-seat passenger, who got out and began shooting, Toohey said.
The car then drove away, leaving one suspect, who ran off.
Latea Bell, the student witness, gave a slightly different account. She said Randallstown football players were arguing with guys who do not attend the school when someone punched a football player.
"One guy punched another guy, and all the friends just joined in," said Bell, who estimated that 20 people were fighting. The brawl ended when shots were fired.
Bell said the dispute between football players and others began the day before when there was a fight in school.
Principal Evans said the dispute might have evolved from an altercation earlier in the week in the school cafeteria.
The school has surveillance cameras outside, one of which overlooks the parking lot. But police said the camera was not working yesterday.
Within an hour of the shooting, police found an expensive black BMW several miles away that fit the description of the car witnesses said the shooters were using.
The car was registered to a company that police would not name. It was not reported stolen.
Police found one suspect shirtless inside a nearby sports apparel store in the 100 block of Reisterstown Road, where he was apparently trying to buy a T-shirt.
A man working at Activewear Outfitters, who would not give his name, said the suspect came inside the store out of breath and went straight to a rack of shirts in the back of the store.
By the time he came to the counter to pay for the shirt, the employee said, police officers were outside and ordered him to come out and lie on the ground.
The suspect surrendered without incident. His identity was not released.
As night fell, family, friends and classmates of the victims gathered at the hospitals.
"I was saying to myself, 'It wasn't him, it wasn't him.' But it was him," said Emanuel Capers, Brown's cousin.
Capers said Brown plans to attend Hampton University next fall.
He hoped to be a member of the school's basketball team.
Nearly 100 distraught, anxious relatives, teachers and coaches paced the hospital hallways.
One football coach was reading aloud from the 23rd Psalm: "Though I walk through the valley of the shadow of death. ... "
"We're all family," said Kenneth Hannah Jr., 17.
"We're with them the whole way."