What clues does the author of An Occurrence at Owl Creek Bridge provide to show that Peyton Farquhars escape is only an illusion?

Although
most readers fall for 's trick and are surprised when Farquhar swings from the bridge after all,
Bierce leaves plenty of clues that the escape is imaginary. For example, although senses may be
heightened under stress, the exaggerated abilities Farquhar possesses strain credulity. While
swimming away in the river, he can see the veins in the leaves of the trees on the shore and the
insects upon them. He can see the eye of the sharpshooter looking at him through the sights of
the rifle. Though frantically swimming away from the bridge, he can observe the actions of the
sentinels on the bridge. A bullet fired at him lodges between his collar and neck, and he
snatches it out.

His walk toward home is similarly impossible and contains
other hints. He sees a "roseate light" and hears "aeolian harps," both
representative of the afterlife. He hears "whispers in an unknown tongue," anto the
Bible passage that begins,...