Be on in danger

Dear folks,

I came across an English expression completely new to me.

I feel I can get something projected by what the author has

to say with the words in red below, but to be true, find it

impossible to figure out the phrase in terms of word usage and grammar.

Please help me out understand the expression from the perspective.

He had suffered from a long life of abuse, but that did not stop Svilicic

from introducing him to their seventeen-month-old daughter, Charlotte.

Brave move on their part. When dogs feel they are on in danger, they

tend to lash and become a threat to everyone around them. Even an

owner that loves and cares for them can become the enemy when a

dog is in this state. Khan had been beaten and starved for most of his life.

The shelter did not think that the dog would ever be fit with a family and

even talked about putting him out of his misery. Svilicic still gave Khan a

chance. The staff in the shelter thought that this woman was being too

trusting with this plan.

[Source: http://www.golferstoday.com/a-mothers-fear-turns-into-relief-after-dog-throws-toddler-across-the-yard/6/]

I assume the expression concerned means "they are in imminent danger."

If it is correct, I do not understand why and how it comes down to the interpretation.

Could anybody enlighten me about the question?

Ray