Had you considered numerological values? If all is One then you are the creator of the experience. But regardless of the source of a message, the message itself has some inherent vibrational value. Rather than focusing on the messenger, perhaps simply focus on any value you can extract from the "message". Whatever you do with what comes to you serves your own growth anyway. If you see demons and attackers at every turn, there's something to learn from that. If you see a benign higher self guiding you lovingly, there's comfort and plenty to go on there, too.
So perhaps you can choose to be the receiver of this event in a meaningful way according to you, the Creator of your life. Consider the possibility that you have far more awareness at another level of Self, and it's speaking to you when you're available and open to it. 4 is an interesting number. It represents the heart, for instance, in this mass consciousness Jung tapped. It is the number of the 4th chakra, in that meme of the paradigm. The 4th ray is the one that indicates harmonizing through chaos, which is essentially what the path of the heart is all about. The color that corresponds to the number 4 is green, a healing, nourishing/nurturing vibration in the spectrum (look at nature).
It could be a symbol representing the next dimension beyond 3D, a step toward limitless. It might represent time or timelessness. Or that unseen realm that we encounter all the time but don't know how to fit into our 3D mindset such as dreams, inspirations, "feeling" knowings rather than intellectually permeating ideas.
There's a wide open field of possibilities to explore for why you would receive this experience. To immediately move toward fear-based concepts indicates a closing off of the all, a narrowing in on one option above all others, and not a very life-enhancing one at that.
Just some ideas. We each have our own inner sense of these things, I thought I'd offer mine. Life, no matter what life it is, speaks to us all the time everywhere, in everthing. In my own heart I know that all life is serving our good. I realize others can't get there for various reasons, but it's a way of facing life that opens so many avenues of awareness growth possibility, rather than the one old path of protect, protect, protect and fight, fight, fight.
There are some things that are constant or consistent and obvious all the time in nature. For me, 4 is inherent nature, and it's everywhere. For another it could indicate "the box", perhaps, and the struggle to get outside it. But again for me, that would also be inherent nature, in motion. Not a negative at all.
I've had a few experiences like you described and for me, I often open inward with curiosity in the moment of seeing such things. Typically a slew of associations impinges on my awareness, often nothing clear, but always a general "tone" of meaning is there as a common thread. Growing one's own symbolic perception is definitely helpful. Eventually you develop an inner resource to draw on no matter what comes your way. After all, manifested life is symbolic. Nothing we see is the thing itself, it's just a symbol representing that thing. The more "clicking" inner sense we make of the symbols we encounter along our way, the more cohesive our outer view of life becomes. We learn to feel our way, rather than just think our way, through it all.
Incidentally, in my own sense of things, all I just wrote up there is learning to SEE. And that was your second message, no? Cool. 
Take or toss, of course.
Sowelu
"The most important decision you have to make is whether you live in a hostile or friendly universe."
~ Albert Einstein
The real voyage of discovery consists not in seeking new landscapes, but in having new eyes. ~Marcel Proust
The evolution of humanity is an evolution of the heart. The path is through the heart.
