Here is how they should have escaped....

Okay I understand everything that happened before the security guard and janitor was killed. After that, it was time to fight. There are 3 of them. At their disposal they had David's car keys to use as a weapon. They had a trash can inside the ATM machine as a weapon. Emily (Alice Eve character) had lipstick and probably other women stuff in her pocket. Finally, they had that liquor bottle to use.

So they go outside and get in a triangle back to back to watch in all directions as they walk out there. Heck once the guy comes near one of them can sneak away and use their jacket to throw over the guy's head to blind him. then you can punch him hard with your keys....wack him hard over the head with the liquor bottle. I also forgot that pen thing they used to strangle that guy they thought was the bad guy they could have used to choke the guy out. They could have fought their way to freedom that night.