Russian agents apparently had Tamerlan Tsarnaev under surveillance last year during his six month trip to Russia. But they lost track of him after a Canadian jihadist – who the Russians believed he was associated with – was killed by Russian police.
From the AP: “After Plotnikov [the Russian-Canadian] was killed, Tsarnaev left suddenly for the U.S., not waiting to pick up his new Russian passport — ostensibly one of his main reasons for coming to Russia. The official said his sudden departure was considered suspicious.”
It’s always worth being cautious with these reports — first of all because all sorts of reports and claims get routed through intelligence agencies but also because I don’t have the sense that the Russian security services, especially when they’re operating in predominantly Muslim regions in the south of the country are particularly discriminating about who counts as a jihadist or a danger. But this latest report sounds more concrete and specific than most of what we’ve heard before.