As Frank walks into Entrance Plaza he is pushed down behind a column by Brad shortly before a shot is heard
Brad: Don't be daydreamin' out here!
Brad: Someone's shooting from the floor above...
Carlito peers through the scope of a huge sniper rifle on the second floor and fires it repeatedly
Carlito embraces his necklace and kisses it then goes back to firing. Frank uses his camera to look around the corner and zoom in on Dr. Barnaby hanging in the hallway. A zombie starts to walk toward Frank.
Frank: Hey, it's the professor!
The zombie behind Frank attacks
Brad: Look out!
A bullet kills the zombie's and splatters blood all over Frank and Brad
Brad: If we don't do something, the professor's gonna to end up zombie chow. I'm going for it. You just worry about staying alive. Got it?
When Frank enters Entrance Plaza, the fight begins. Carlito Keyes is armed with a powerful sniper rifle this time, and will be much more difficult to get close to than last time.
It is recommended that Frank does not follow Brad, because Brad is a diversion and if Frank is next to Brad,
Carlito's attention is focused on Frank too, instead try to surround Carlito. Brad is a big key to defeat Carlito; when he attacks Carlito, it will provide Frank with an open opportunity to strike, because Carlito's back will be turned. Alternatively, if Brad is damaging Carlito severely, let the DHS agent do most of the work.
If Frank has a firearm, head up either of the escalators right beside Frank's starting position, and then head around to the right, and take cover behind the corner of Outta Sight store on the left. From here, Frank should be able to target Carlito on the opposite walkway without exposing himself to his fire.
Alternatively, acquire a sniper rifle and shoot Carlito's head from behind a pillar. If positioned correctly Carlito will not be able to shoot Frank but Frank can shoot this psychopath.
Quickstep, Katana, or sledgehammer strategy
Bring two Quicksteps and a katana or sledgehammer to the fight. This drink increases Frank's running speed dramatically. Frank has to be level 10 or higher or Carlito will slaughter Frank. Make sure Frank has Orange Juice or Milk(s). After the cut scene run along to the far end of the plaza and go the escalators. By doing this Carlito is now surrounded by both Brad and Frank from either side. Frank can use the individual support pillars, to advance on Carlito and avoid his gunfire. When close to Carlito, drink the quickstep, equip your Katana and run at him. Slash, Slash, Slash. Strike him quickly, because if Frank stands around too long after attacking Carlito, the psychopath will counterattack with the blunt end of his sniper rifle. Carlito should be defeated relatively quickly. His bullets should miss Frank as Frank is moving too fast.
Hockey stick strategy
Go up the stairs, go into Shootingstar Sporting Goods and grab a 3-5 Hockey Sticks and go to the closest pillar and go into aiming mode, and shoot off all of the pucks at Carlito. Make sure to line up your shots first. Repeat until Carlito has been defeated.
Once Carlito has been defeated a second time, Brad and Frank rescue Dr. Barnaby, and return to the Security Room - but Brad's been shot and needs medical assistance. Jessie is able to patch him up, but he will need a medical kit.