? I can’t make sense of your sentence.
Damned spillcheck...
The officer’s noticed Crook when he arrived in the area outside the checkpoint, using a range finder.
They thought this was suspicious and put out a radio alert telling everyone to keep an eye out, but when they tried to follow him they lost him in the crowd.
He never attempted to pass through the checkpoint.
Next report I’ve seen was an officer who saw him on the roof, with the rifle. The building he was on was outside the security perimeter, and he could approach it without passing through the checkpoint.