Why No Taser?

I've been highly critical of overuse and inappropriate taser use by police. But here's a situation where a taser might have been used instead of lethal force, but was not.

A man entered his Sikh temple in suburban Cleveland early Thursday, raised a meat cleaver near two members preparing for morning prayers, and was shot and killed by police, authorities said. ... The two men readying to pray fled and returned with officers, who were confronted within a minute by the man, again with the cleaver raised, the chief said. He kept moving toward officers and was shot.

The story doesn't say the man made a sudden charge at police, just that he kept moving toward them. Why not drop him with a taser instead of killing him? This is exactly the sort of situation where a taser should be used as an alternative to lethal force. With multiple officers present, it would still have been possible to kill him should the taser have proven ineffective. I know I'm second-guessing a crisis situation, and there might have been other factors involved. But it seems that a taser should have been a viable alternative. As Obama would say-- let me be clear. The shooting was definitely justified. Police have every right to defend themselves against the potentially lethal threat of a bladed weapon. But was the shooting necessary, when a non-lethal tool widely employed by police might have gotten the job done?