How do we create a MySQL one-time event that executes immediately?

mysql> Create table event_message(ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT, MESSAGE VARCHAR(255) NOT NULL, Generated_at DATETIMENOT NULL);
Query OK, 0 rows affected (0.61 sec)

mysql> CREATE EVENT testing_event ON SCHEDULE AT CURRENT_TIMESTAMP DO INSERT INTO event_message(message,generated_at) Values('Hello',NOW());
Query OK, 0 rows affected (0.00 sec)

mysql> Select * from event_message;
+----+---------+---------------------+
| ID | MESSAGE | Generated_at        |
+----+---------+---------------------+
| 1  | Hello   | 2017-11-22 17:05:22 |
+----+---------+---------------------+
1 row in set (0.00 sec)