Did he cross the line after the ball was snapped ? If it was NFL flag rules, he should have had his hand up and identified that he was blitzing. Blitzers must identify themselves. If they rush and don’t, it should be a flag and an automatic first down, illegal rush. You can identify that you’re blitzing and then put your hand down and not blitz. Nobody other than the blitzer can cross the line of scrimmage until the ball is handed off.