Chicago police said Friday there has been a 14% drop in violent crime overall in the city compared to last year - with the two most violent districts seeing a 33% drop in violent crime - and there have been 234 less people shot this year.
"We are foundationally changing the way we fight crime in Chicago", Chicago police Superintendent Eddie Johnson said in a statement on Friday.
CNN was first to report earlier this year the formation of the team, which the ATF called in internal documents the "Chicago Crime Gun Strike Force".
Chicago police officials said the unit would focus on preventing illegally possessed guns from flowing through the city and on targeting people repeatedly involved in gun crimes, both of which have always been cited as drivers of the violence.
Shortly after he assumed office, President Trump tweeted "If Chicago doesn't fix the disgusting "carnage" going on, 228 shootings in 2017 with 42 killings (up 24% from 2016), I will send in the Feds!".
The new set of agents will work with counterparts from the Chicago Police Department and Illinois State Police on a strike force to solve shootings and arrest gun traffickers, according to the Sun-Times.
The decision is the Trump administration's solution to dealing with the city's "crime and killings", which, according to Trump, "have reached such epidemic proportions". "1714 shootings in Chicago this year!" There were 1,935 shooting victims in the city during the same period past year.
Weather: Things are heating up
Dew point temperatures will be in the 60s and lower 70s and that means it will be an uncomfortable day outdoors. Heat indices will remain in the 90s for holiday weekend and by Monday they are forecasted to be back near 100°.
Chicago Mayor Rahm Emanuel's office confirmed Friday that the ATF agents were in the city and praised the police department's progress in addressing the city's challenges with violence.
"The most critical factor to our success is the strength, training, and morale of the Chicago Police Department and all of our law enforcement partners".
Local officials, in response to Trump's earlier comments, have said they had asked his administration for more help tracking illegal guns and for more federal gun prosecutions.
"Murders are way, way too high", he said.
Sessions last week pledged federal assistance to 12 cities to help them develop individualized, long-term strategies to fight violence. "In many ways, the policies in Chicago have not been working". But Chicago was not among them.
It was not immediately clear whether the announcement Friday will come with additional federal agents or a reorganization of existing resources. The Chicago Police Department's Organized Crime Bureau and the ATF's Chicago Field Office will work with the team, as will prosecutors from the U.S. Attorney's Office as well as the state's attorney's office.