Chicago packed more violence into its reputation as one of America's bloodiest city by chalking up 56 shootings with 12 deaths over the holiday weekend.

"It's surreal," a Chicago woman told the Chicago Tribune after racing to help a man gunned down in her neighbourhood. "You can never get used to this.

Among the wounded was Jacele Johnson, 4, who was struck in the head by a mystery gunman who opened fire from a vehicle that pulled up alongside her family's car. Her 17-year-old cousin in the car was also wounded, and a 15-year-old girl standing on a sidewalk nearby was shot in the forehead. All remain in hospital in fair to critical condition, reports the Sun-Times.

It was the most violent Memorial weekend in Chicago in a decade, reports CBS. Most of the violence occurred in the city's south and west side neighbourhoods where gangs are the most active.

Last year over the same weekend, shootings in the city killed six people and wounded 22. Shootings in Chicago are up 24% this year over 2013, and homicides are up 18%. There are more murders in Chicago than in New York City and Los Angeles. In 2012 police recovered more guns there — 7,624 — than in NY and LA combined.

Chicago wasn't the only American city rattled by gun violence. At least 32 people were shot, two fatally, in Baltimore over the long weekend. That made this month, with a total killing tally of 35, the deadliest month in Baltimore since 1999.

This is dashcam footage of a shootout in Chicago over the weekend. Police responded to calls that shots were fired but there were no known injuries reported and no arrests were made. YouTube