"I am three meters from the scene."
Translation:Estoy a tres metros de la escena.
It took a lot of googling, but here you go - it's just a standard use of the preposition "a":
We can express distance between two points with Estar + a: Mi colegio está a dos kilómetros de tu casa. (My school is two kilometers away from your home).
"De" is the word to use here. Best I can tell, "desde" usually implies movement, range or time (from here to there, from one to ten, from June to September). It can also mean "since". Most other situations call for "de", but there is some overlap. See the article below.
"As a general rule, it can be said that desde more strongly indicates motion from a location, although it is frequently used where no destination is given."
Google "ser vs. estar"
This page has my favorite explanation:
Imagine: Soy -being something more on the permanent and unchangeable side, like: I am short, i am dark skinned, i am American... etc. Soy americano
Estoy -more on a temp basis. Like a mood change, state of being. I am angry (right now) but could be Happy later, I am walking (but could run later) etc. Estoy enojado, Estoy feliz, Estoy caminando,
Hope it helps.