About 500 spectators were packed around the Kingsessing Recreation Center's outdoor basketball court Monday night, cheering on an adult league playoff game.

Then, at halftime, a thug in a red and black baseball hat loped across the court and fired a .40-caliber handgun 11 times into the bleachers, wounding six people.

As of Tuesday afternoon, none of those 500 witnesses was saying much to police.

So, at an afternoon news conference, Mayor Nutter, along with Police Chief Charles H. Ramsey and a dozen other police and city officials, stood on the still blood-spotted court and offered a $20,000 reward, imploring residents to come forward and identify the "coward" who shot the spectators.

"We need the community's help and support. Someone knows who it is. We want that information today. We want that person in custody today. Then he can stand up as the coward he is and pay the price for the crime committed," Nutter said.

Given the "incredible nature of the crime," Nutter said he decided to dip into a $500,000 crime reward fund created by City Council earlier this year.

"We will not tolerate this kind of insane, asinine, idiotic behavior at any of our facilities," he said. "They are safe havens . . . they are off-limits to this kind of heinous behavior. We will not stand for it."

Of the gunman, Nutter said: "We're going to find your little butt and lock you up."

The mayor said that he had played at the recreation center as a child and that the gunman had broken a "principal community code" by violating its safety.

About 8:50 p.m., one minute into halftime of an over-17 semifinal game, the shooter walked down a crowded ramp leading to the court and opened fire on a crowd of people on the sidelines, police said. He hit five men and one woman, none of them players, between the ages of 18 and 23, and sent the large crowd of spectators running through the streets.

"It was crazy," said one neighbor, who heard the shots from her home across the street. "People were diving behind cars and shielding their babies."

Five of the victims were shot in the lower extremities, said Inspector Dennis Wilson of Southwest Detectives, and one man was shot in the stomach and is in critical condition. The intended target was shot in the attack, Wilson said.

Police are still interviewing victims, who all remain hospitalized.

The gunman, who is black, believed to be around 22 years old and about 5-foot-9 and 150 pounds, escaped the court through a hole in a fence, police said.

Two 12th District police officers who were working the game gave chase but lost sight of him in the crowds about a block from the shooting, police said.

The center, which has numerous basketball courts, a baseball field, a tennis court, and a boxing ring, was one of 20 city facilities designated for extra weekend hours earlier this month as part of the new city teen curfew.

It is the second shooting at the recreation center this summer.

On July 5, about 10 p.m., a 20-year-old was shot in the back as he hung out on the court after a basketball game. Police had made an arrest in the case just hours before Monday night's shooting.

That shooting was over drugs, police said, and not related to Monday's shooting.

Tuesday morning, a custodian at the center poured bleach over the bloodstained bleachers. Coach Cantrell Fletcher, 51, ran his 12-and-under squad, the Super Sneakers, through drills. They are competing in a league championship this weekend, and he did not want to cancel practice.

"It's safe here in the day," said Fletcher, who has been coaching at the center for more than 30 years. "The older kids, they come and do their business at night. They like to have a lot of people around. I guess it builds their ego."

One of Fletcher's players, Daiquan Copeland, 12, a seventh grader at Henry C. Lea Elementary School, had worried that practice would be canceled when he saw the shooting on the news.

"That's all he cared about, was practice, practice," said his father Antron Copeland, who watched from the sidelines with his younger son, Quadir, 7. The little boy stopped dribbling his basketball and pointed out the ground.

"Here's more blood, Dad," he said.

Contact staff writer Mike Newall at 215-854-2759, mnewall@phillynews.com, or @MikeNewall on Twitter.