BIRMINGHAM, Ala. (AP) — An Alabama teacher who used a hypothetical assassination of President Barack Obama as an example in a geometry lesson says he is sorry.

Jefferson County teacher Gregory Harrison released a statement Thursday saying his comments were inappropriate, and he called them a "very serious error."

Harrison previously was suspended with pay, and school officials say he's now giving up 10 days of salary but likely won't have to miss more time in the classroom. He's also getting a formal reprimand and must undergo diversity and sensitivity training.

Harrison was teaching a lesson on tangent lines and angles earlier this month when he discussed the possible gunshot assassination of Obama.

The Secret Service interviewed Harrison but determined there was no credible threat. No charges were filed.