Boston police commissioner Ed Davis has confirmed that Dzhokhar Tsarnaev killed his own brother Tamerlan by running him over with an SUV while officers were trying to arrest him.

Ed Davis told CNN he believes Tamerlan Tsarnaev, 26, died from being hit and dragged 40 feet by his own brother Dzhokhar.

Doctors revealed that Tamerlan Tsarnaev had been shot and appeared to have suffered a bomb blast, however his wounds from the tires of his stolen SUV appeared the most severe.

However, a medical examiner must still confirm the cause of death.

Authorities are investigating whether Dzhokar Tsarnaev ran over his brother Tamerlan as part of a suicide pact so that neither of them could be put on trial

According to law enforcement sources, Boston Marathon bombers Tamerlan and Dzhokhar Tsarnaev were determined not to be taken alive.

Authorities are reportedly investigating whether Dzhokar Tsarnaev, 19, ran over his brother Tamerlan as part of a suicide pact so that neither of them could be put on trial.

Later, as police closed in Dzhokar Tsarnaev reportedly put a gun in his mouth and pulled the trigger.

“These guys did not have an exit plan after the bombing, and from the way they have both ended up it looks like they planned on never being taken alive,” said a law enforcement source.

“Why else would this kid drive over his brother? It does not make any sense until you realize he also tried to take his own life. They had some sort of suivide pact worked out so they would not be taken alive.”