What we know to date about Kilimnik, courtesy of a Politico story from August 2016:

https://www.politico.com/story/2016/08/paul-manafort-ukraine-kiev-russia-konstantin-kilimnik-227181

Kilimnik did not hide his military past from his new employer. In fact, when he was asked how he learned to speak such fluent English, he responded “Russian military intelligence,”

"It was like ‘Kostya, the guy from the GRU’ — that’s how we talked about him,” said a political operative who worked in Moscow at the time. “The institute was informed that he was GRU, but it didn’t matter at the time because they weren’t doing anything sensitive.”

"There was no secret that [Kilimnik] had been in the intelligence services back in the Soviet Union. He would talk about it. Others on the campaign — Paul, Phil Griffin, Rick Gates — they were pretty open about his background.”

Updated reaction?