How to configure 2 buttons to play 2 different sounds at the same time

This code has 4 buttons; 2 buttons play different sounds and 2 buttons stop the sound. Only one button can play its sound at a time. Once another button is pressed the sound from the button that was pressed is stopped for the new button to play its song. How make my code play 2 buttons at the same time? Code is below thanks?

mport UIKit
import AVFoundation
class ViewController: UIViewController {
var audioPlayer = AVAudioPlayer()

    override func viewDidLoad() {
    super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}


@IBAction func hatingschool(sender: AnyObject) {
    let alertSound = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("s", ofType: "mp3")!)
    
    do {
        // Preperation
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
    } catch _ {
    }
    do {
        try AVAudioSession.sharedInstance().setActive(true)
    } catch _ {
    }
    
    // Play the sound
    do {
        audioPlayer = try AVAudioPlayer(contentsOfURL: alertSound)
        audioPlayer.numberOfLoops = -1
    } catch _{
    }
    
    audioPlayer.prepareToPlay()
    audioPlayer.play()

}

@IBAction func stophatingschool(sender: AnyObject) {
    audioPlayer.stop()
    audioPlayer.currentTime = 0
}
@IBAction func drums(sender: AnyObject) {
    let dd = NSURL(fileURLWithPath: NSBundle.mainBundle().pathForResource("dsd", ofType: "mp3")!)
    
    do {
        // Preperation
        try AVAudioSession.sharedInstance().setCategory(AVAudioSessionCategoryPlayback)
    } catch _ {
    }
    do {
        try AVAudioSession.sharedInstance().setActive(true)
    } catch _ {
    }
    
    // Play the sound
    do {
        audioPlayer = try AVAudioPlayer(contentsOfURL: dd)
        audioPlayer.numberOfLoops = -1
    } catch _{
    }
    
    audioPlayer.prepareToPlay()
    audioPlayer.play()

}

@IBAction func stopdrums(sender: AnyObject) {
    audioPlayer.stop()
    audioPlayer.currentTime = 0
    
}

}