234688
On 15 April 2005 , whilst carrying out a special operation in Grozny , Medvedev and two comrade s of the Vympel unit of the FSB were killed .
 Grozny, Medvedev, FSB
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Grozny, Medvedev, FSB