CHICAGO (CBS) — In the wake of one of the most violent weekends of the year in Chicago, Mayor Rahm Emanuel and Chicago Police Supt. Eddie Johnson angrily lashed out at armed criminals who repeatedly open fire in the city, often shooting innocent unintended victims.

“We have a heavy heart. Our souls are burdened,” the mayor said, repeatedly choking up as he spoke at a South Side police station.

The mayor and the superintendent spoke out Monday morning after at least 12 people were killed and 54 others were wounded in shootings from 6 p.m. Friday through midnight Sunday night.

Chicago police said dozens were shot in six mass shootings during a seven-hour span early Sunday, with at least four people shot in each of those attacks. Those six shootings alone left a combined three people dead and 28 others wounded.

“What we saw this weekend, it just rips at everything that I believe in,” Johnson said of the bloodshed. “This isn’t a widespread issue among citizens of this city. This is a small subset of individuals who think they can play by their own rules because they continue to get a slap on the wrist when we arrest them.”

Earlier this weekend, Chief of Patrol Fred Waller blamed gang members who often target one specific person in a group, but end up wounding several innocent bystanders.

“When it’s very hot outside, we have multiple areas with crowds. … An offender, or some type of rival gang sees a large group of people,” he said. “They take advantage of that opportunity, and they shoot into a crowd, no matter who they hit.”

Johnson said, while investigators have “really good leads” on several of the shootings, police have not made any arrests. However, he lamented that too often witnesses do not come forward to identify the shooters.

“We can do better. Certainly CPD can do better, but at the end of the day, the members of CPD don’t go to bed with these individuals at night, they don’t wake up with them in the morning. It’s very rare we actually witness this stuff. Somebody knows who did it. They do. They know that,” he said.

The mayor said solving the city’s violent crime problems is about more than reforms at the Chicago Police Department, or providing more jobs in the city.

“There is a shortage of values about what is right and what is wrong,” Emanuel said. “There’s something more at stake, and all of us know that this is not Chicago, what we saw.”

Johnson was more direct in his reaction to this weekend’s bloodshed, angrily lashing out at the shooters.

“You know what I never hear? I hear people holding us accountable all the time. I never hear people saying ‘These individuals out here in the streets need to stop pulling the trigger.’ I never hear that. I never hear that. They get a pass from everybody, and they shouldn’t,” he said. “It’s the same individuals that continuously commit these crimes. Where’s the accountability for them?”

After this weekend’s bloodshed, Emanuel has faced criticism from several challengers in the 2019 mayoral election

Former Police Supt. Garry McCarthy, fired by the mayor in 2015, accused Emanuel of continually ignoring violent crime on the South and West sides.

“Instead of facing this horrific condition head-on, with community-based solutions for this human carnage of African-American children, this mayor wants to talk about how the murder rate is going down. Who’s buying that given what we just witnessed this weekend?” he stated.

McCarthy also took a shot at the mayor’s press conference on Friday to announce expansion plans for the Chicago Riverwalk.

“While grieving families were filling emergency rooms, Rahm Emanuel was holding a news conference about a $10 million dollar expansion of the River Walk downtown, while people are dying in the neighborhoods,” McCarthy said. “Mayor Emanuel is out of touch with reality. He is out of touch with our neighbors in the neediest communities and he is failing them…. to death.”

Former Chicago Police Board President Lori Lightfoot said the city is facing a “public health crisis,” and Emanuel “cannot sit this out.”

“As mayor, I will confront our city’s gun violence crisis directly and with empathy rather than remain silent as more than 70 people are shot in a single weekend,” she said. “Taking on gun violence goes far beyond policing: it’s about ending poverty and reversing decades of disinvestment through quality schools, career training, social services, and jobs in neighborhoods that have been ignored for too long.”

Former Chicago Public Schools CEO Paul Vallas called the weekend’s violence “absolutely horrific,” and said it is the direct result of the Emanuel administration’s failure to fill police vacancies in Chicago during his two terms in office.

In vowing to rehire as many as 400 retired police detectives if he is elected, Vallas also criticized the Emanuel administration for having “one of the worst clearance rates for homicides and other violent crimes among America’s major cities.”

“This is a crisis in which four out of five killers in Chicago are literally getting away with murder. Is it any wonder this past weekend witnessed more than 60 shootings in the city?” he said.