05/30/2012 02:12 pm ET

Andre Alejandro, Chicago Man, Charged In Pizzeria Shooting Death Of 13-Year-Old

Police have charged a Chicago man with first-degree murder after gunshots fired into an Uptown pizzeria killed a 13-year-old boy.

Ivan Alanis was fatally shot around 2:20 a.m. while eating pizza at Laurie’s Pizzeria and Liquors, 5153 N. Broadway, with his sister.

Witnesses say Alanis argued with Andre Alejandro, 22, before Alejandro left the restaurant, then returned with a handgun and fired through an open door, CBS Chicago reports. Alejandro then fled the scene, and was later arrested by police.

Alanis was struck in the face and taken to Illinois Masonic Hospital in critical condition, where he was later pronounced dead, according to ABC Chicago.

Police allege that the conflict between the two was gang-related, and witnesses say Alejandro, a member of the Gangster Disciples, shouted gang slogans before firing, according to the Chicago Tribune. Police told the newspaper that Alanis was affiliated with a rival gang, a claim the teen's family denies.

"He was a good person," father Rogelio Alanis told the newspaper.

Alejandro is due in court Wednesday.

Meanwhile, less than a mile away, a 23-year-old employee of a neighborhood bar and grill located in the 5000 block of North Clark Street was stabbed in the back early Wednesday while taking out trash, the Tribune reports. He was treated and released.

Eleven people were killed and at least 40 hurt by gun violence in Chicago over the Memorial Day weekend. The violence prompted Mayor Rahm Emanuel and Chicago Police Superintendent Garry McCarthy to discuss the city's anti-gang strategy, as they believe most of the shootings were gang-related.