Police discovered a massive arsenal stashed in a Staten Island ex-con’s home, including armor-piercing incendiary rounds, a trove of guns and almost 200 fireworks, officials said.

All told, there were 20 shotguns, handguns and rifles hidden throughout the Midland Beach home of Anthony Cortese, 47, almost half of which were stuffed in a closet in his 11-year-old son’s room.

Cortese was charged with criminal possession of a weapon and endangering the welfare of a child.