Step back a minute and take in the whole situation: terrorist bombing, assassinated cop, carjacking, robbery, shoot out with police involving more bombs, and then escape by one of the suspects.
Its clear to me that the only goal the suspects had in mind was to cause harm to society in any way possible. So what does society do? It reacts in order to nullify that threat.
When the city goes on lock down, that is to help the police do there job, but it is also to secure the citizens. Given how the situation played out, it is very possible that the suspect(s) would have killed anyone they came across. So the lockdown was justified.
"Stay inside because there is a guy out there willing to fucking kill anyone he sees and he has bombs". Its justified in my opinion.