Evidence presented during the third day of the trial of alleged Boston Marathon bomber Dzhokhar Tsarnaev showed him make a purchase at a Whole Foods in Cambridge just minutes after two explosions went off on Boylston Street.

Caitlin Harper, a Whole Foods employee who formerly worked at a Cambridge branch near Central Square that Tsarnaev bought milk from at 3:14 p.m. on April 15, testified that she handled the store’s surveillance footage and examined it with FBI agents to confirm Tsarnaev’s identity in the shot.

The bombs exploded at 2:49 p.m.

Though the video simply shows Tsarnaev purchasing a dairy product, then leaving the store only to return and exchange the milk for another carton, it’s the lack of any emotion that makes the footage so chilling.

Tsarnaev acts as though nothing happened some 25 minutes prior.

The defense team cross-examined its first witness on Wednesday, a FBI forensic audio and video analyst who compiled surveillance footage from establishments on Boylston Street. The timestamps on the video, he testified, were approximate and did not accurately reflect the actual time because they’re contingent on when the system is turned on.

In this case, however, the prosecution produced the receipt produced from Tsarnaev’s purchase which contains an actual timestamp pitting him at the Whole Foods at 3:14 p.m.

And because the defense admitted Tsarnaev’s direct involvement in the bombing during opening statements, it’s even eerier that while watching this footage viewers know that Tsarnaev consciously and deliberately detonated one of two bombs that combined killed 3 and injured 264.