Express JS 4 sends console.log output

This is very strange in that Express JS is sending the console.log output to the client without res.send being used.

Calling the /api POST endpoint shows the "Hello" from the parseJSON back to the client.

How can I get this to stop?

var express = require('express');
var bodyParser = require('body-parser');

var app = express();

app.use(bodyParser.json({
    limit: '50mb'
}));

app.use(bodyParser.urlencoded({
    extended: false
}));

app.get('*', function(req, res, next) {
    var err = new Error();
    err.status = 404;
    next(err);
});

// handling 404 errors
app.use(function(err, req, res, next) {
    if (err.status !== 404) {
        return next();
    }

    res.send(err.message || '** 404 error **');
});

app.post('/api', function(req, res) {
    parseJSON(req.body);
    res.status(200).end();
});

app.listen(80);

function parseJSON(jsonData) 
{
    console.log("HELLO");
}