Also from that article:

A highly placed rebel, speaking to the AP this week, admitted that rebels were responsible. He said a unit based in the hometown of ousted President Viktor Yanukovych, made up of both Russians and Ukrainians, was involved in the firing of an SA-11 from near Snizhne. The rebel, who has direct access to the inner circle of the insurgent leadership in Donetsk, said that he could not be named because he was contradicting the rebels’ official line.