Question

the moment he switched the television there a silence in the room. we all looked each other not knowing to react

Answer 1

There are four omissions in the sentence-

They are switched on, was a silence, looked at each and knowing how to.

So, the sentence is -

the moment he switched on the television there was a silence in the room. We all looked at each other not knowing how to react.  

Answer 2

$\textbf{\large{Answer-}}$

the moment he switched $\textbf{\underline{on}}$ the television there $\textbf{\underline{was}}$ a silence in the room. we all looked $\textbf{\underline{at}}$ each other not knowing $\textbf{\underline{how}}$ to react.