On Sunday, Chicago police chief of patrol, Fred Waller admitted authorities were "behind the eight-ball" in trying to get those responsible for the surge in attacks behind bars. "It is unacceptable to happen in any neighborhood of Chicago".
As of 3:15 p.m., at least two other people had been killed and 25 more had been left wounded in Sunday shootings.
Asked why, if the good outweigh the bad, members of the community are not stepping up to help identify shooters, Johnson said: "That's a question we've been asking for quite some time, so, listen, that's something they have to do better at".
Police blamed much of the carnage on gangs, which run rampant in some of the city´s poorest and predominantly minority neighborhoods on the west and south sides.
Police called it one of Chicago's "most violent weekends".
"Considering Rahm Emanuel has been mayor since 2011 and murders have gone up, what we've seen is a mass genocide in the streets of Chicago", Caldwell said, adding that unless President Trump intervenes, the only way to mitigate the violence would be to vote Emanuel out of office.
The former New York City mayor also tweeted his support for Chicago's former superintendent, Garry McCarthy, referring to him as "Jerry" and calling him a "policing genius".
"These shootings are not random, they're fueled by gang conflicts".
The death toll from this weekend's violence in Chicago has risen to 12.
Emanuel didn't immediately respond to McCarthy or Giuliani. "It's the same people pulling the triggers".
"We continue to send a message that it's okay to commit these crimes by not doing anything as a community".
The violence peaked early on Sunday, including one shooting on the city's South Side that wounded eight people.
US President Donald Trump has repeatedly vowed to intervene in Chicago, and past year he said that crime and killings had reached "epidemic proportions" in the city.
More than 1,600 people have been shot in the city this year, including three children who were recently wounded while playing basketball.
Chicago saw 650 homicides in 2017, down from 768 in 2016.
Although the drop was significant, the total still exceeded the combined the number of killings in New York City and Los Angeles, which are the two USA cities bigger than Chicago.
In a statement, McCarthy called himself a "proud Democrat" and distanced himself from Giuliani's views and "the misguided, divisive tone and policies of Donald Trump".
Chicago Mayor Rahm Emanuel dismissed that hot weather is to blame.