The Tsarnaev brothers, Tamerlan and Dzhokhar, gained their fame in a very notorious way. That is crashing the Boston marathon and turning it into a mass crime scene. The police definitely had no idea about the suspects, but thanks to CCTV captures, they eventually identified them.
However, the identification of the suspects was only the first part of the manhunt because the brothers immediately tried to bail out from the police. Again, their plans were foiled by technology in the form of the mBrace system of Mercedes-Benz.
According to the story of CNN, the Tsarnaev siblings hit the road as soon as they realized that they are about to be caught. So, they carjacked a Mercedes-Benz M-Class to help them evade the authorities. The owner, a Chinese businessman named Danny, was also held hostage during the process. As it turned out, they chose the wrong vehicle because the auto was equipped with the advanced mBrace system.
When the brothers stopped for gas, their hostage immediately took the opportunity to run away from his captors and he reported the incident to the police. The perpetrators of the Boston bombing took off before the police arrived.
Using the mBrace technology of the car, it was traced later and the police pinned both suspects down. A shootout ensued which left the older Tsarnaev dead. Then, although the younger one escaped, he was captured after some time.