McCall's old team already cleaned up that loose end. That was the scene where the two guys found a ringing phone buried under their couch before the apartment exploded.

Yes, sure, but those were just the henchmen. I meant whoever ordered that hit.

Or did I miss something, and Dave and co. were also behind that murder too?

I don't think they ever addressed who ordered Dave's team to perform the hit at the beginning of the movie, but Susan was murdered because Dave knew she was going to figure them out.

Those henchman were hired to kill Susan so that Dave could have an alibi with video evidence showing he had gotten off the elevator on a different floor right before the murder took place.

I'm not sure I understand what motive these guys had. "Because they were sick of the system?"

@Tyler-A-Arse said:

I'm not sure I understand what motive these guys had. "Because they were sick of the system?"

There was that scene where Denzel visits his old army friend's house; he explains it with the "there's no good or bad guys, just unfortunates" or something like that. They're doing the same thing except rather than the government telling them who to kill, it's someone else. And they get paid a lot more. So yeah, they were sick of the system I guess