[LouieFisk]

“The CNN story quotes an LEO saying that the shots heard were probably by law enforcement.”
==
That would make sense of the conflicting accounts.

[justlurking]

There's another article here:

http://www.nbcnews.com/news/us-news/active-shooter-reported-ohio-state-university-campus-n689076

It says that one person was arrested, as well.

Based on all the bits of info, I'm going to speculate a bit:

1. A co-conspirator set off the fire alarm.
2. As people were evacuating, the other conspirator drove into the crowd of people.
3. One of the two conspirators attacked people with a machete.
4. The guy with the machete was killed by police.
5. The other was identified and arrested. If he was the driver, he would be easily identified. If he was the guy pulling the fire alarm, someone must have seen him do it.

It may be a couple of days before we get the full story,