Was Ukrainian prosecutor Viktor Shokin prosecuting Burisma?

 https://edition.cnn.com/factsfirst/politics/factcheck_3fae078e-8724-4c28-9340-2c154688af43

CLAIM

Trump said that the Ukrainian prosecutor Joe Biden had pushed to oust, Viktor Shokin, was "prosecuting" the company where Hunter Biden sat on the board, Burisma.

CONCLUSION

Shokin was not prosecuting Burisma.

EVIDENCE

While there had been an investigation of the company, Shokin's former deputy, Vitaliy Kasko, has said that it was dormant at the time of Joe Biden's intervention. (The former US ambassador to Ukraine, Marie Yovanovitch, and the Deputy Assistant Secretary of State for European and Eurasian Affairs, George Kent, testified in Trump's impeachment inquiry that Shokin was corrupt; the US and its allies had made a coordinated effort to oust him.)