Ping and MotorShield work independently but not together.

The following code works perfectly util I uncomment the lines motor1.run and motor2.run

Then the motors start running and the Ping Sensor no longer seems to read any info.

What am I missing?

The following video shows what I mean.

Once the two lines are uncommented, the motors start running but the Ping no longer receives and input.

#include <AFMotor.h>

AF_DCMotor Motor1(1);
AF_DCMotor Motor2(4);


const int serialPeriod = 250;       // only print to the serial console every 1/4 second
unsigned long timeSerialDelay = 0;

const int loopPeriod = 20;          // a period of 20ms = a frequency of 50Hz
unsigned long timeLoopDelay   = 0;

// specify the trig & echo pins used for the ultrasonic sensors
const int ultrasonic2TrigPin = 8;
const int ultrasonic2EchoPin = 9;

int ultrasonic2Distance;
int ultrasonic2Duration;


void setup()
{
    Serial.begin(9600);
  
    // ultrasonic sensor pin configurations
    pinMode(ultrasonic2TrigPin, OUTPUT);
    pinMode(ultrasonic2EchoPin, INPUT);
 
}


void loop()
{
    debugOutput(); // prints debugging messages to the serial console
    
   if(millis() - timeLoopDelay >= loopPeriod)
   {
        readUltrasonicSensors(); // read and store the measured distance        
        timeLoopDelay = millis();
   }
   if (ultrasonic2Distance<=200)
   {   
     Motor1.setSpeed(255);
     Motor2.setSpeed(255);
//     Motor1.run(FORWARD);
//     Motor2.run(FORWARD);
   }
   else
   {
     Motor1.setSpeed(0);
     Motor2.setSpeed(0);
//     Motor1.run(BRAKE);
//     Motor2.run(BRAKE);
   }

}


void readUltrasonicSensors()
{
    // ultrasonic 2
    digitalWrite(ultrasonic2TrigPin, HIGH);
    delayMicroseconds(10);                  // must keep the trig pin high for at least 10us
    digitalWrite(ultrasonic2TrigPin, LOW);
    
    ultrasonic2Duration = pulseIn(ultrasonic2EchoPin, HIGH);
    ultrasonic2Distance = (ultrasonic2Duration/2)/29;
}


void debugOutput()
{
    if((millis() - timeSerialDelay) > serialPeriod)
    {
        Serial.print("ultrasonic2Distance: ");
        Serial.print(ultrasonic2Distance);
        Serial.print("cm: ");
        Serial.println();
        
        timeSerialDelay = millis();
    }
}

I think that pin 8 and 9 are already used by the Adafruit Motor Shield.
You should try one of the analog pins, you can use those as digital pins as well.