He was already in the process of accelerating before you engaged on him and once you did he stopped his car. Also, how did he stop like he was "going to drop" on you? In order for him to comply he has to stop his car either way and the way he stopped his car seems pretty normal for someone trying to comply, he didn't turn his car away from you or anything like that.
So if I engage someone in Sofia and my gang member sees one of them at salt flats air field, it would be RDM for them to shoot since its more than 1km?
What if one of them were to drive down from Sofia after engaging there without anyone in my gang knowing, should my gang member still not shoot at them if he sees him more than 1km from where the engagement started?
I do have it bound, and I tried using it on my gang member while my titan still wasn't working and it didn't do anything. I'll try verifying my game though.