According to Watertown police chief, Edward Deveau, the elder Tsarnaev was alive when his younger brother ran him over in the Mercedes SUV they carjacked earlier.
In an interview with CNN's Wolf Blitzer, Deveau provided further details of the killing and capture of the Boston Marathon bombers. With regard to the first gunfight Thursday night, Deveau said that after they let the SUV's owner go, his cellphone remained in the vehicle which allowed police to track the car.
When the Tsarnaevs arrived at the site of the initial gunfight, the brothers were in separate cars, apparently, one of them being the carjacked SUV. They encountered a lone officer who Deveau states was instructed to wait for backup. The Tsarnaevs however, got out of the cars and began "unloading" on the police officer in his car.
Backup arrived and a massive gunfight ensued, including more homemade explosive devices. Eventually Tamerlan came out from cover and approached the officers, firing as he did. He then ran out of ammo and officers took their chance.
He runs out of ammunition, the bad guy, and so one of my police officers comes off the side, tackles him in the street trying to get him handcuffed, there's two or three officers handcuffing him in the street...at the same time, at the last minute, they obviously have tunnel vision, very, very stressful situation, one of them yells out "look out" and here comes the black SUV, the carjacked car, directly at them. They dive out of the way and he runs over his brother, and drags him a short distance down the street—In effect killing his brother?—Yes, that's what we think.
Hours before his death, Tamerlan reportedly called another estranged uncle living in Maryland, Alvi Tsarnaev, and asked for forgiveness for their lack of communication.