(Reuters) - A mother watched on Thursday as a man approached the Chicago south side restaurant where she works and opened fire, killing her two sons and two other men in a shooting that police described as gang-related retaliation, media reported.

A lone gunman opened fire just before 4 p.m. local time at the Nadia Fish and Chicken restaurant in the South Shore neighborhood, killing Dillon and Raheem Jackson, who were found outside the establishment when police and rescue workers arrived, the Chicago Tribune reported.

“I can’t go on, my life is over. I’m ‘bout to ... kill myself,” their mother told the Chicago Tribune as she wept, still wearing a red apron from her job at the restaurant as her sons’ bodies lay nearby. “I was standing right here in the window, they killed ‘em right in front of me.”

Two other men were found dead inside restaurant, the Chicago Police Department said in an email to Reuters.

No arrests have been made in the shooting, police said.

The shooting was believed to be gang-related retaliation “from another incident,” a NBC affiliate reported, citing police spokesman Anthony Guglelimi.

The men were among the nine people shot on the city’s south side on Thursday, including a pregnant woman who was found dead earlier in the afternoon in her apartment about a mile from the restaurant, the Tribune reported.

That shooting did not appear to be related to the restaurant killings, the newspaper reported.

Homicides are down by about 10 percent so far in 2017 in the third-largest U.S. city after a particularly deadly year in 2016, when there were 60 percent more homicides than in 2015, the Tribune reported.