The soldier's way

Tasso, Gerusalemme Liberata book 13, stanzas 38: our heroine has been transformed into a tree

‘He [Tancred] drew his sword at length, and with full force
Struck the tall tree; O wonderful! The wound,
As bursts a fountain from its sylvan source,
Gush’d forth with blood, and crimson’d all the ground.
Chilld horror seized the knight: yet, fix’d to sound
The mystery to its depth, and desp’rate grown,
Again he struck; when, hollow and profound,
As from a vaulted grave, in piteous tone,
Murm’ring he heard within a spirit deeply moan.
[The Jerusalem Delivered of Torquato Tasso, translated into English Spenserian verse by J H Wiffen (2 vols, 1824-5), 2:40]

He doesn't realise there's something odd about the tree after one sword-hack? Or he does, but hitting the creature a second time with a sword is the only way he knows of investigating further?