I got this video from the Islamic Jihad saraya.ps front page.
The caption brags that this mortar launcher is targeting the Kerem Shalom crossing, from which the majority of Gaza's food, medicine and other aid arrives.
Despite the barrage of rockets and mortars, Israel opened the crossing on Sunday to allow aid to get to Gazans. Since this is a new video, it appears that Islamic Jihad deliberately is trying to shut the crossing down, to cause a "humanitarian crisis" in Gaza.