Initially, the police thought it a murder-suicide; however, after the initial investigation and after questioning witnesses in the building, they knew it wasn't, they got an ID of the perp, found him, and were questioning him when the second shooting occurred. It seemed reasonable to not lockdown the campus if you thought you had the perp in custody.
Regardless of the circumstances, can you think of any municipality in the US that shuts down the entire city for a shooting?
Even if you just limit such a response to cities of 26,000 or less, expectations of such a reaction are extremely low..
Here in Kansas City, MO (more than 26K population..) the city would be in "lock-down" mode half of the year..
The (liberal) public's reaction is completely over the top on this..