OK.
Now at least we know that there were actually attackers.
Now for the numbers:
FRONT ENTRANCE
Witnesses place 4 attackers storming WestgatE from the front entrance and wrecking carnage at Art Caffe and Urban. This group is the lot captured in the CCTV footage.
ROOFTOP
Multiple witnesses place at least 2 different gunmen attack from the rooftop where a children’s cooking competition was going on. These freely hurled grenades "like maize" and slaughtered many there according to eyewitnesses.
BASEMENT
A "command and control centre" in an unidentified vehicle driven to the car park some time in advance of the attack was setup. The death of Ghanaian poet Kofi Awoonor, who was shot in his car as he was preparing to leave, confirms the presence of armed gunmen in the basement from the beginning of the assault.
At 2.30pm Witnesses on the car park roof saw at least two men, who they believe to have been attackers, changing into casual clothes near the tent where the cooking competition was judged. At this point there was no police cordon and no screening process for survivors coming out of the mall. Intelligence officials believe that at least two attackers were able to escape in the confusion..Yet another attacker by this witness account escaped later that evening -
http://www.youtube.com/watch?v=P6F1yWAGKhU
Deducing from the above, it's my belief there were well more than the 4 attackers captured in that video. It is clear some got away by changing clothes and melting away with the crowd specifically on Saturday as trapped victims.