There are multiple references in yesterday's hit to shadows and shifts. This could lead to either MEC or Elvaiz. I know you want to scream, 'No, but Elvaiz said he was the doctor!" But that doesn't necessarily follow. Elvaiz may have been saved by the doctor, if the doctor hadn't known he was Mafia, and then after killing off the doctor, could have claimed to be in order to get us to trust him. In addition, he certainly made a big deal about getting the SK out of the way... it took a LOT of heat off of Tinct that night. Of course, he had to sacrifice Tinct the next night to stay alive. But where better to hide but in plain sight? Claim you're the good guy then sabotage everyone from behind the scenes!
Next, the obvious references to shifts and shadows from yesterday's hit. These would point in MEC's direction. There's also the fact that in his bio, he states that he is proficient in any matter requiring stealth and espionage. That would make him a good candidate to perform a murder as described from Day 5.
There's also Cache, who can indeed produce purse-sized items from out of a little black hole. A length of wire, perhaps, or a piece of concrete. Perhaps even a knife.
Today's hit had a few references to texture... such as the following :
as her companion’s leg slipped between hers, stopping her stride and spilling her on to the ground
These could quite possibly point to our slippery, stealthy shapeshifter Marcus.
Then again, from yesterday's hit, the references to shadows also stick out quite boldly. Both Elvaiz and Marcus are creatures of shadow. One because he claims to dwell in them, and the other because he's self-admittedly stealthy.
Now, on to the actions of the transport driver: is there any possible connection between then direction he chose to drive in after the energy blast hit the street and the fact that the driver is Marcus? (See the end of Day 5's transit)... Marcus is the transport driver. We are being led toward the sentinels. Could he have knowingly driven us into an ambush, expecting that we'd be picked off one by one eventually?
Food for thought.
My suspicions fall today on Marcus and Elvaiz, who could just be slick enough to pull off a lie that he's the doctor, while tackling us from behind one by one.