The slaying of Hadiya Pendleton, as she stood with friends Tuesday afternoon in a park, came on a day that saw the city's 40th, 41st and 42nd murders of the year, according to police. It continued an uptick in homicides that began last year when more than 500 people were killed. The majority were gang-related shootings on the city's troubled south and west sides.
On Wednesday, Ms. Pendleton's death was raised at a White House news briefing and became the subject of a news conference with Chicago Mayor Rahm Emanuel, who called the sophomore honor student "what is best in our city."
Chicago Police have struggled to overcome what they say is an entrenched code of silence that they blame for the low homicide-clearance rate. Mr. Emanuel said: "If anybody has any information, you are not a snitch, you're a citizen. You're a good citizen in good standing if you help."
Then a man with a gun jumped a fence surrounding the park and ran at them firing. The group scrambled to get away, and Miss Pendleton—who police say wasn't affiliated with a gang—was shot once in the back and killed, Mr. Purkiss said.
"The area is a hangout for gang members and it is believed the offender mistook the group for gang members and fired at them," Mr. Purkiss said. "By all indications [Miss Pendleton] was an unintended victim." The shooter jumped in a car and drove away. There have been no arrests.
Semiautomatic weapons are banned in the city of Chicago, as are stores that sell guns. But guns are available in neighboring suburbs, and gun violence here goes hand in hand with the city's gang culture and a membership police estimate at 100,000.
At a news conference Tuesday, Chicago Police Superintendent Garry McCarthy said that through the first three weeks of January, officers in two of Chicago's 22 districts seized more illegal guns than were collected in all of New York City in the same period.
This January has been the deadliest in the city since 2002, while 2012 saw the most murders since 2008, according to the Chicago Tribune.
Miss Pendleton's murder comes as lawmakers in Washington debate a ban on semiautomatic weapons following the massacre of 20 school children in Newtown, Conn., last month.
At the White House on Wednesday, Mr. Obama's spokesman Jay Carney said: "We need to take action on common-sense measures that do not infringe upon our Second Amendment rights...but that makes sure that we're doing everything we can in a responsible way to reduce this violence, to protect our children, including Hadiya Pendleton and others."
Around the same time, a memorial service was being held in Miss Pendleton's school. Her classmate Mariah Williams said, "Everyone was crying...there were teddy bears and pictures in front of her locker."
A few hours later, Miss Pendleton's aunt described her niece as a young woman with boundless energy and high ambition. She hoped to study pharmacology and journalism at Northwestern University, and was eagerly planning her sweet-16 birthday party in June.
"She was a cheerleader, a basketball player, a volleyball player—you name it, she wanted to do it," said Kimiko Pettis.
Miss Pendleton left on a bus for Washington last Friday with her school's marching band to perform at several events around Mr. Obama's inauguration.
"It was her first time in Washington," said Ms. Pettis. "She was so excited."
