Ron has evidence been given as to how he could have mistaken his gun for his laser?
It is many hours later, Jane, and someone else may have answered this. From what I understand, the defense witnesses, and Mehserle himself, all stated there was a lot of confusion. It was noisy and several different troublemakers were being handled by different groups of officers. At some point someone said Mehserle had unholstered his stun gun and had it out a couple of times. I haven't seen any actual testimony to indicate the sequence of events or how Mehserle, himself, recounted what happened and why he thinks it may have happened.
Some co-workers cannot get past the fact that three officers were needed to take down Grant. Actually, I believe there were three officers per troublemaker. One person resisting arrest with all his might can be difficult to handle even when two officers are handling him.
Others contend that with Grant face down, there was no need to stun him...and that the shooting had to be racially motivated.
People believe what they want to believe regardless of how incomprehensible it might be.