Kill zone? Really? So you set up a near ambush? Are they delivering well aimed fire at you? If not why would you engage? I can see the headline now. Armed citizen stops drive by shooting Even if the press doesn't publish your name you're making yourself a target for retaliation. If it's not your job to intervene why would you even consider it if it wasn't necessary to protect your life? Why stick your head up from behind cover? You don't have the rest of your squad with you to help you gain fire superiority.
No, you find yourself caught in a near ambush of sorts however. Since, as you said, you don't have the rest of your squad with you to throw grenades at the enemy and assault though the objective, your strategy has to be modified to immediately seeking cover and beyond that the situation will evolve and dictate your next moves and you're at the mercy of fate.
Your immediate goal would be to seek cover.
We all agree on that. But that doesn't mean you should hide behind a vehicle's engine block and close your eyes and try to retain control of your bodily functions until it's all over. If you're carrying, you should prepare to fight if necessary and try to remain situationally aware to the maximum extent possible. Situational awareness is always critical but especially when unknown people are shooting around you/near you for unknown reasons.
Seeking the closest bestest cover is your top priority here. Exposing yourself from good solid cover should only happen if necessary to save your own life.
Numerous people were shot by Charles Whittman during the
University of Texas Tower Shooting when they broke cover for various reasons including leaving cover/concealment to aid others or for having sub-optimal cover.
Paul Bolton Sonntag-They took refuge behind a construction barricade, but when Sonntag abruptly stood, Whitman shot him in the mouth, killing him instantly.
Claudia Rutt tried to reach Sonntag as Wheeler attempted to restrain her; a shot passed through Wheeler's left hand and struck Rutt in the chest.
Roy Dell Schmidt-Schmidt took cover with others behind his car some 500 yards (460 m) from the tower, but after about 30 minutes stood up in the belief he was out of range, and was immediately shot in the abdomen.
Billy Paul Speed-At 12:08 pm, Patrolman Speed was with another officer and others behind decorative balusters on the South Mall when he was shot through a gap in the masonry.
If it becomes necessary to break cover in order to move to a new position for whatever reason, it would be best if you had a buddy that was covering your movement. That's a good reason to carry a BUG right there btw, so you can hand it to your wife or whoever.