Murder in Kadara Port
Location: Kadara
The second time you enter the Kadara Marketplace, you'll find guards milling around a dead body.
You might assume this is just one of the people they were beating to death earlier, but no, this one's murder. Unsanctioned murder, even. Scan the body, then follow your marker to meet Reyes in the Slums.
He'll fill you in on the background and his own theories on the murder, then give you a crimescene to investigate.
Closing this conversation actually closes the mission, but immediately segues into A People Divided.