Step son's mom died and I'm not sure how to comfort him

Im not sure what to say honestly. Idk if I tell him I'm sorry or? My step son didn't really like his mom. How my husband got full custody in court was because we had videos that he had recorded of his mom yelling at him. Calling him a dumbass. Throwing a plate at him. She would humiliate him in front of friends. On his 13th birthday he called us crying because his mom was yelling at him in front of his friends saying if he's gonna cum all in the bed, out his own wet dream sheets in the wash. She humiliated him a lot and he always said he hated her. They both got into a car accident and how the accident happened was she ran a red light while yelling at him about something on his visitation with her. He doesn't even remember what she had yelled at him about. I want offer him support but idk how. He went to her funeral but only stayed about 20 minutes and wanted to go. I really don't know how to support him.