My duck became really aggresive someone help anyone plz?

he used to be sweet all the time but at times aggresive(he is a mallard) but now everytime i take him out of his cage he chases me and not specieficly me like my mom and my sister too and he was always like that when i take him out but now all he wants to do is attack us he isnt the sweet duck i knew he was before. and the weird thing is everytime he is ready to attack he bites his leg lol. can someone give me any tips or why he like chews his leg everytime he does this plz i want to train him to be nice again