It isn't Felicity who passes closest to him. It's Jet. At that moment, Tom realizes that he has two options, equally risky; either who could try and do hell unto a cyborg, knowing that the fight will likely end up one-on-three, or he could try and retreat, knowing they might pursue him anyway.

He trusts his gut instinct, which is to try and reduce the number of enemies as quickly as he can. He lunges forward out of the darkness, knife brandished, and plunges it into Jet's face from behind, hoping to hit brain (that's the only surefire vulnerability). He throws his arm around Jet's neck and clamps on, keeping the man from throwing him or falling forward, as a shield for just a moment before he makes his next move.