He poked the crucified JESUS in the side and was then heard to say: "Truly this was the Son of God!" as the blood and water gushed out. Truly side-splitting.
The New Testament doesn’t go into much detail here, but we can reveal that, according to tradition, St LONGINUS was miraculously cured of bad eyesight by a splash of the Holy Blood.
He was instantly converted, left the army and became a persecuted monk instead. At some point his teeth and tongue were forcibly extracted but that didn’t stop him miraculously praising the Lord in the clearest tones.
Finally the authorities lost patience and lopped off his head. And by an amazing coincidence, a splash of blood from his nicked neck cured the chief persecutor of blindness.
Meanwhile the original spear or lance is now in the Holy Relics collection at St Peter’s in Rome — if it wasn’t stolen by Hitler or some collector. The lance as a symbol of power has become much more important than LONGINUS who ought to feature as the Patron of Conspiracy Theories.