I have a number of reasons why i think its
Saul. He did serve time in prison before he joined the army so its possible that he could have come into contact with one of
the mallers during his time inside, he could possibly owe them a favour or something.
Secondly, we dont really know what happened with him after the mallers spotted him. All we know is he got back to
the tower. He was only on a scooter or something like that and we know
latch and
Scratch had a fast sports car. They would have easily caught him and perhaps ( like i mentioned before ) one of the mallers recgonised him and maybe called in a favour?
Thirdly, why did he leave his bike outside the tower. Fair enough the lights were probably on in the tower, but seeing the scooter he got away on would have helped confirm it was the right apartment block.
Fourthly ( is that even a word?? ) on the night of the attack on the tower, Saul was supposedly out cold due to the drink. I think he was the one who fired the shot and was actually just faking it. Also, how did the mallers know that the people in the tower actually had a CB? They had to know that it was a CB they had in the tower as they brought their own and told the tower what channel to turn it to. They wouldnt have know what kind of communication device Saul had unless they actually caught him.