Narcisco Gatica, 19, of the 2400 block of West Armitage Avenue, and Berly Valladares, 21, of the 2600 block of West Cortland Street, were each charged with one count of first-degree murder and one count of attempted murder, according to Cook County State's Attorney's Office spokeswoman Tandra Simonton.
Gatica is believed to be a member of the Maniac Latin Disciple street gang. Valladares is decorated with tattoos that say "Grim Reaper" and "Thug Life," according to the Sun-Times.
A surveillance video from a house located next door to the shooting shows one of the alleged gunmen pulling a weapon from his jacket before opening fire.
The suspects were arrested separately Tuesday morning.
Valencia, a 21-year-old senior political science major and a star student at DePaul University, was shot and killed at a Halloween Party in the Humboldt Park neighborhood early Sunday morning.
Another DePaul senior, 21-year-old Daisy Camacho, was shot in the neck and was in stable condition. Camacho, a psychology major, was Valencia's girlfriend.
Gatica was an univited guest to the party and became upset by the "perceived slight" of being asked to leave. He went to Valladares' residence to get a gun, telling him that needed it to shoot someone, Det. Joseph Salemme said during a Wednesday afternoon press conference.
Shorly after getting the gun, a TEC-9, Gatica returned to the party and began shooting erratically, letting four to six bullets fly through the air.
In a statement, police said Valladares admitted to detectives that he supplied the gun to Gatica.
A dorm adviser, Valencia is among students currently profiled on the university's Web site.
"He was the kind of student we liked to spotlight," said DePaul spokesman John Holden.
In a statement, Valencia's family said it is "heartbroken by the loss of their cherished son, brother, mentor and friend. He led by example, the family said, volunteering at the Chicago Public Schools and for the Obama campaign, as well as traveling to Columbia on a humanitarian mission.
"His ambition, idealism, intelligence, enthusiasm and commitment made him a natural leader, who strived to change the world. He aspired to have a career in politics and to serve as an example to the Latino community. Frankie inspired and mentored those he touched," the family said.
Valladares and Gatica are expected to appear for a bond hearing on Thursday at 1 p.m.