Alex was not going to repeat the same mistake twice in such a short period. The first time could be because he did not expect it, but now that he knew, he wasn't about to fall for the same trick twice.
Throughout the entire time he was fighting this group of students, his guard was always up. He may have appeared relaxed and easygoing at a glance, but his senses never relaxed.
Whoever that archer was, he/she was bound to come after him again. Even if that person wasn't, there were bound to be others.
When he picked up a faint whistle of something travelling through the air, Alex did not need to think twice and evaded the arrow that zoomed past his head a second time.
However, unlike the one before, this one continued on its path and hit a student directly facing Alex, taking him out.
As soon as he dodged the arrow, he noted its trajectory, and without looking to see the shooter, spun around and threw his spear in the person's direction.