Boston Marathon bombing: FBI releases video of Dzhokhar Tsarnaev's movements before and after deadly blasts

Chilling footage shows the Boston bomber buying a pint of milk after the blast

The jury at the Boston Marathon bombing trial were shown a video timeline of Dzhokhar Tsarnaev's movements before and after the explosion that killed three people in April 2013.

The video, compiled by the FBI and shown on day three of the trial, shows Tsarnaev and his late older brother and alleged mastermind of the bombings, Tamerlan, walking along the Boston Marathon route, both wearing large backpacks as they approach the area where the bombings occurred.

In one particularly chilling scene, Tsarnaev is seen standing alone outside the Forum restaurant, just yards away from Lingzi Lu, 23, and 8-year-old Martin Richard. Both Lu and Richard would die moments later.

The clips show Tsarnaev dropping the bag in a crowd of people, close to several children, including Richard's sister, Jane, who lost a leg in the explosion.

After the first bomb explodes, most bystanders look towards the blast, yet Tsarnaev walks in the other direction and moments later the second bomb goes off.

Prosecutors allege that Tsarnaev detonated the second bomb and the video shows him running through the crowd following the blast.

While Dzhokhar fled the scene, running along Boylston Street and turning north onto Fairfield Street, his elder brother, Tamerlan, walked calmly down Boylston and north along Exeter Street, a block east of Dzhokhar's exit.

Around half an hour later, Dzhokhar is seen walking into a Whole Foods store over the Charleston river in Cambridge buying a carton of milk.

Jurors also heard from Danling Zhou, the close friend of the late Lingzi Lu, who is seen standing near to Tsarnaev before the fatal blasts. She said that Lu grabbed her arm after the first blast and said, "What happened?" and "What should we do?" The second blast, which killed Lu, went off before Zhou could answer her best friend.

Jessica Kensky also testified before the court. She lost her left leg on the day of the bombing. Her right leg was amputated in January of this year because it had failed to heal from injuries sustained in the blast.

Jessica Kensky and Patrick Downes complete the marathon one year after the bombing (Getty)

Her husband, Patrick Downes, lost a leg in the blast. The couple were taken to separate hospitals in the aftermath of the attack and did not see each for two weeks, the AP said. They completed the race the following year in wheelchairs.

Tsarnaev, 21, is accused of killing three people and injuring 264 in the blasts that were set off at the finish line of the race on April 15 2013.

Prosecutors allege the brothers carried out the bombings in retaliation for the US for wars in Iraq and Afghanistan. Tsarnaev's defence admit his involvement in the blast but argue that the he was influenced by his older brother. Tamerlan was killed during an attempted getaway a few days after the bombings.

Additional reporting by the AP.