he is people agressive?
like how agressive? what does he do when he meets people?
is he agressive with you and your family? people he knows?

it's this a new thing or has he always been like this?

if it's a new thing i would suggest having him looked over by a vet and have a blood test and urine and fecal tests done to rule out any health problems that could be making him act this way

if he is perfectly healthy then I would suggest some NILF training http://www.pets.ca/articles/article-dog_nilf.htm

and contact a behaviourist to have them evaluate him....he might just be a mentally unsound dog and would be better of being humanely euthanized so he does not harm a person