weird opening

so i play this guy at the club and he plays this (by the way i'm white hes black) e4 c5 Nf3 Nf6. is this an error? shouldn't i just go e5 after that then if he goes d5 press c4? my database is on my other computer and its not running at the moment. any ideas? he fallows up with Nc6 and e6 if i play Nc3 then d4

Yeah, play e5; see the shredderchess.com database.

thanks

also try chessgames.com