Nodejs giving me download instead of html response

Here is my code:

var express = require('express'),
      app = express.createServer(express.logger());
app.use(express.bodyParser());
app.get('/', function(request, response) {
    var name = request.param('name', null);
    response.header('Content-Type', 'text/event-stream');
    var t = setInterval(function(){
        response.write('Hello World by '+name+' (using http-1.1 streaming data!)<br />');
    }, 2000);
    /*request.socket.on('close', function() {
        clearInterval(t);
    }); */
});

var port = process.env.PORT || 5000;
app.listen(port, function() {
    //clearInterval(t);

  console.log("Listening on " + port);
});

I am using express because I am testing this in heroku and I used the guide there. So when I open the app I get a download popup with the data in the file (downloaded) instead of the html (dom) response.

What did I do wrong? (is it a browser problem?)

Edit:
@Joe, has solved my initial problem but yet, I have two questions:
1) Why i don't need to insert a 'correct' content type? (of streaming?)
2) Why does this code out put only after along time (about half a minute).?