Florida school shooting suspect Nikolas Cruz reportedly etched swastikas onto the rifle magazines he was using during his alleged killing spree.

The 19-year-old brought over 300 rounds of ammunition into Marjory Stoneman Douglas High School on Feb. 14 — more than half of which he left unused, according to reports.

Investigators have no idea why Cruz stopped shooting that day or why he chose to leave the ammo behind.

Law enforcement sources told CBS News and CNN that authorities found 180 rounds inside Stoneman Douglas. Cruz fired off about 150.

Officials said the young man confessed to the early-afternoon massacre and told them that he had “brought additional loaded magazines to the school campus and kept them hidden in a backpack until he got on campus to begin his assault.”

All of the magazines that Cruz carried, including the one found in his rifle, reportedly had swastikas etched onto them.

Investigators believe the former Stoneman Douglas student may have been trying to set up a “sniper’s perch” — based off a broken window that was discovered at the scene.

For some unknown reason, though, Cruz dropped his weapon and decided to flee. He was later captured without incident.

Cruz faces 17 counts of premeditated murder. He is accused of gunning down 14 students and three teachers.

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