BOSTON (CBS) – Federal investigators have revealed new details about the Boston Marathon bombings and the chaotic events that followed later in the week.

Dzhokhar Tsarnaev, 19, was formally charged Monday in the attacks.

A sworn affidavit from FBI special agent Daniel Genck was filed with the criminal complaint and it sheds new light on how investigators found Tsarnaev and his brother Tamerlan.

Read: The complaint (.pdf)

Here are some highlights from the affidavit:

THE SECOND BOMBING

Genck said security camera video shows the brothers carrying large knapsacks as they walked onto Boylston Street from Gloucester Street around 2:38 p.m., 12 minutes before the bombs went off.

“Approximately 30 seconds before the first explosion, (Dzhokhar) lifts his phone to his ear as if he is speaking on his cell phone, and keeps it there for approximately 18 seconds. A few seconds after he finishes the call, the large crowd of people around him can be seen reacting to the first explosion. Virtually every head turns to the east (towards the finish line) and stares in that direction in apparent bewilderment and alarm. Bomber Two, virtually alone among the individuals in front of the restaurant, appears calm. He glances to the east and then calmly but rapidly begins moving to the west, away from the direction of the finish line. He walks away without his knapsack, having left it on the ground where he had been standing. Approximately 10 seconds later, an explosion occurs in the location where Bomber Two had placed his knapsack.”

THE CARJACKING

Near midnight on Thursday, about seven hours after the FBI published video and photos of the bombing suspects, there was a carjacking in Cambridge.

“A victim of the carjacking was interviewed by law enforcement and provided the following information. The victim stated that while he was sitting in his car on a road in Cambridge, a man approached and tapped on his passenger-side window. When the victim rolled down the window, the man reached in, opened the door, and entered the victim’s vehicle. The man pointed a firearm at the victim and stated, “Did you hear about the Boston explosion?” and “I did that.” The man removed the magazine from his gun and showed the victim that it had a bullet in it, and then re-inserted the magazine. The man then stated, “I am serious.”

“The man with the gun forced the victim to drive to another location, where they picked up a second man. The two men put something in the trunk of the victim’s vehicle. The man with the gun took the victim’s keys and sat in the driver’s seat, while the victim moved to the front passenger seat. The second man entered the victim’s vehicle and sat in the rear passenger seat. The man with the gun and the second man spoke to each other in a foreign language.”

“While they were driving, the man with the gun demanded money from the victim, who gave the man 45 dollars. One of the men compelled the victim to hand over his ATM card and password. They drove to an ATM machine and attempted to withdraw money from the victim’s account. The two men and the victim then drove to a gas station/convenience store in the vicinity of 816 Memorial Drive, Cambridge. The two men got out of the car, at which point the victim managed to escape.”

EXPLOSIVES EXAMINATION

“A preliminary examination of the explosive devices that were discovered at the scene of a the shootout in Watertown and in the abandoned vehicle has revealed similarities to the explosives used in the Boston Marathon. The remnants of at least one of the exploded IEDs at the scene of the shootout indicate that a low-grade explosive had been contained in a pressure cooker. The pressure cooker was of the same brand as the ones used in the Marathon explosions.”

DZHOKHAR TSARNAEV FOUND

“He had visible injuries, including apparent gunshot wounds to the head, neck, legs, and hand.”

“One April 21, 2013 the FBI searched DZHOKHAR TSARNAEV’s dormitory room at 7341 Pine Dale Hall at the University of Massachusetts at Dartmouth, pursuant to a search warrant. The FBI seized from his room, among other things, a large pyrotechnic, a black jacket and a white hat of the same general appearance as those worn by Bomber Two at the Boston Marathon on April 15, 2013, and BBs”