Asking for some clarity about my late uncle's situation

Assalamu alaikum. My uncle passed away at 29 after getting badly burned while saving my cousin's life. He wasn't someone who practiced his faith regularly, but he did believe in Allah. From an Islamic viewpoint, could someone in his position be counted as a shaheed? Are there any teachings about whether someone like him might still enter Jannah even if they weren't very practicing? Also, would the questioning in the grave still be relevant in a case like this? I'm just looking for some comfort and understanding here, not to start any arguments. JazakAllah khair.