Updated 10 p.m. 2/9/2015

CHICAGO (CBS) — A 13-year-old boy was shot and killed in front of his sisters in the Belmont-Cragin neighborhood late Sunday, and his family said the shooting might have been the result of a post on Facebook.

Following interviews with witnesses, police know the identity of the suspect they are seeking, a source tells CBS 2.

Anthony Diaz was shot around 10:30 p.m. Sunday near the intersection of Grand and Austin avenues. He was pronounced dead at Mount Sinai Hospital about an hour later.

“I know my son got killed today. That’s very sad. I wish this violence stopped,” his mother, Laura de Domenico said Monday morning.

Anthony’s family said he and his 16- and 17-year-old sisters went out Sunday night to confront other girls about a dispute on Facebook. They expected a fight, but not a fatal shooting.

Anthony’s mother, Laura de Domenico said her 16-year-old daughter is in a street gang, and has had legal problems.

“I’m against violence. I’m a hard-working mom, and I don’t even know where she gets this from, but that’s her hobby: running away, and fights,” de Domenico said. “She always had this problem with fighting. I always tell her not to take him, because he’s not streetwise at all.”

But her daughter did take Anthony along Sunday night. While he used his phone to record a fist fight between his sister and another girl, someone else walked up and started shooting. Anthony was shot in the chest.

Anthony’s parents said they’re not sure what sparked the dispute on Facebook.

De Domenico said her daughter’s first words after learning Anthony had been killed were about retaliation.

“First thing, I walk home, she’s like ‘How he’s doing?’ I’m like, ‘he’s gone.’ The first thing, ‘I’m going to get revenge.’ I’m like, ‘No, you ain’t getting no revenge.’ I mean, take this as an example for all you guys, teenagers, because you guys, for stupid things, a lot of people getting killed, and your brother’s not coming back,” de Domenico said.

De Domenico said she will cry for her son for the rest of her life.

Anthony’s stepfather, Ralph Otero, said his stepson was a good student, and loved basketball.

“I’m devastated. The mom is devastated. We’re all in shock. My pastors are very devastated, because he’s a good kid. He was a good kid, honors student, and outgoing person,” Otero said. “All I ask is for justice. … I don’t wish them harm. I don’t wish them anything bad, but unfortunately, we’re on this Earth, and we’ve got to pay for our mistakes.”

Friends and family gathered Monday night at Grand and McVickers  where Diaz was shot. They announced a $1,000 reward for case-solving information.

An account has been set up at Chase Bank in the young man’s name in order to pay for funeral expenses, family members said.