Looks like MadScientest has the answer with the 'Dry Stun' that you also mentioned earlier, gbpackfan. Also makes sense that that they tased him 4 time, which they couldn't do if they'd fired the darts (single use cartridge) unless they had multiple units.

I think the answer here is that they grossly underestimated CE's ability to withstand pain. I'm not surprised - and I would guess that many NFL lineman (and a certain QB) would be able to 'shake off' a dry tasing a lot more quickly than the cops would expect!