As they approach his house, Tim fires at them from the second floor window. The men fire back blindly. Tim kills one of them. The other takes cover. He finally spots Tim and fires at him.
Is it clear from the highlighted sentence that the men fire back at Tim even though they don't know where he is?
Could back be misunderstood to mean that they were shooting behind them?
It is understood as you intended. It's well written.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.