Everything that happened in bond markets today, happened before noon.  Whether this was a factor of European markets contributing to the volatility or simply another afternoon during August isn't readily apparent, but both likely contributed. 

Treasuries were slightly stronger in the overnight session.  10's and MBS were both back to yesterday's best levels at the open.  The morning data only proved to be a minor speedbump in the grand scheme of things (stronger Housing Starts caused temporary weakness).

It wasn't until stocks were open for the day and headlines hit alluding to potential Ukraine/Russia deescalation that the weakness flared in earnest.  It was fueled on several occasions by large block trades in Treasury futures.  These happen every day, but when trading activity is as light as it was today, they have a bigger effect.

At the end of the day, we're left with charts that look much more dramatic than the actual price levels.  Fannie 3.5s are only down 2 ticks as we approach the close and 10yr yields are up 1.5bps to 2.402.