Delete item with partition key & range key - DynamoDB

I have a DynamoDB table with the following attributes:

SubscriptionsTable:
    Type: AWS::DynamoDB::Table
    DeletionPolicy: Retain
    Properties:
      TableName: ${self:custom.subscriptionsTableName}
      AttributeDefinitions:
        - AttributeName: eventName
          AttributeType: S
        - AttributeName: hookUrl
          AttributeType: S
      KeySchema:
        - AttributeName: eventName
          KeyType: HASH
        - AttributeName: hookUrl
          KeyType: RANGE

I would like to delete an item according to its hookUrl and eventName. That's the code of my repository:

const deleteSubscriptionFromRepository = async ({
  hookUrl,
  eventName,
}: {
  hookUrl: string;
  eventName: SubscriptionEventName;
}) => {
  const mapper = getDatabaseMapper();

  try {
    return await mapper.delete(Object.assign(new SubscriptionModel(), { hookUrl, eventName }));
  } catch (e) {
    throw new DatabaseAccessError(e.message, 'deleteSubscriptionFromRepository');
  }
};

Instead of using directly the DynamoDB client, I'm using the DataMapper from '@aws/dynamodb-data-mapper';

But I'm receiving the following error:

  DatabaseAccessError: The number of conditions on the keys is invalid

How is that possible to delete an item according to its partition and range key? What I'm doing wrong in the above code?