Circumstances of unlocking the case: This case may become available while you are exploring the game world freely. Somewhere around The Bowery or the Industrial District Batman may be contacted by Alfred, who will inform him of the interception of the SOS signal, and will suggest checking it out.
You start this investigation in the tall building (the above screenshots) located in the Western part of The Bowery. You need to make it over to the balcony of the building , and you can do it by approaching it from the North-Eastern side, while using the hook. After you reach your destination, approach the burning flare, thanks to which you will determine that this is a police trap set for you.
The police chopper will soon crash in obscure circumstances and you will, of course, need to examine this in detail. Glide towards the blazing wreck. After the Batman determines that there are no survivors, turn on the evidence scanner.
Start by scanning the corpse that you have found near the crashed helicopter, which will result in a preparation of the base version of the events.
Disable the evidence scanner for a moment a use the hook again, to reach the balcony above, where you have found the burning flare. Scan the area next to the balustrade, thanks to which you will work out an improved reconstruction.
The next step is to find the chopper's tail rotor. Rewind and fast forward the reconstruction using the appropriate keys/triggers. Performing this action will allow you to locate the element shown in the screenshot, which you are occupying at the moment (walk around the main building from any side). Scan the rotor and learn the results of the investigation again.
Now you need to locate the places that the shot has been fired from. Return to the area on the upper balcony, where you have been scanning a bit earlier, climb onto the balustrade and star the process of modifying the reconstruction again. Thanks to this you will notice the red line. Glide along that line, thanks to which you will reach the rooftop of one of the lower buildings, shown in the screenshot.
Enable the evidence scanner again and scan the SWAT team member's corpse. Performing this will lead to an unexpected conclusion, i.e. that the responsible for the chopper crash is, most probably, Deadshot himself.
The next action to perform during this investigation, is to locate the spot from which Deadshot took the shot. Keep the detective vision turned on and follow the line that shows the trajectory of the bullet. Along your way, use gliding and the hook to your aid which will ultimately take you to a small catwalk.
Scan the bullet case on the catwalk and find the radio frequency written down on it. Finally, use the Cryptographic Sequencer, set the crosshair in the orange circle and hold down the key/button shown in the screenshot to decode the transmission. Listen now for the conversation with Deadshot.
Note! At this point, the game will unlock an additional side-mission connected with Deadshot. You can find its description in the chapter entitled Most Wanted and although you do not need to take to it straight away, it will be possible to complete it without any additional preparations.