Another idea using Bullet could be to:
-Add a second Tilemap just for collisions or an alternative is by using Tiled_BG
-Add the solid behaviour to it
-Close the grid area by surrounding the grid with thin lines around the 4 edges of the grid
-Set the sprite bullet settings "Bounce of solids" to Yes
-And every (5 or X) seconds set "sprite.Bullet.Angle of motion" to a random(360)
Example:
The red lines are the collisions, which is a Tiled_BG with solid behaviour.
One thing that I see in your video is that the sprite comes from outside the grid so you may want to turn off collisions for the sprite temporarily until is inside the grid then you turn the collision on.
Both behaviours are good for this type of job.