But there isn't. Military and police are very different resources, which is why they're not sent to do each other's jobs. They could give it a go in an emergency, but they're very far from interchangeable.
To implement your plan, you would have to have the army authorised and willing to deliberately kill civilians in your own country. You said yourself it was a show of force, which means that you have to be willing and able to apply that force. In the case of the army, the force is deadly force. Even when military forces are there to keep the peace, they're there to keep the peace by force - the message is "keep the peace or be killed". Military forces can be deployed in a non-military capacity where a quick response by a large group of people well trained in working together is useful. Disaster relief, for example. But not as force to replace police. The "force" part would mean deploying military forces in a military capacity.