Call and take a note.

Information about the player helps a lot here.

Pre flop AJo makes a good 3 bet versus an UTG open in position.

When villain checks the turn I would make a small value bet while your kicker still counts. As played I would make a tight fold on the river without being sure if villain was likely to do this with AT.

I think the 3 bet is decent, vs more reggy players especially. Thing is we don't know much about this player.

His stack size suggests a casual, but does he like to just call with any two that look kinda pretty preflop?

Usually only AT is behind. I might make a tough fold personally but it's quite villain dependent.

Inexperienced players don't think about ranges or how they interact. An inexperienced player is not thinking about your cards, likely they are looking at an AX hand on a AAxxx board and thinking nuts. Call and take a note. If it is AQ AK A2 A6 22 66 ok cool hand wd, but by definition bad players play bad. Please don't fold here. He will turn over A9 and think he has been coolered then tell people about some gross spot in 10NL where he flopped trips and the other guy had him kicked.