Bombing suspects were after MIT officer’s gun, officials say

WASHINGTON--Tamerlan and Dzhokhar Tsarnaev allegedly shot and killed a Massachusetts Institute of Technology police officer Thursday because they wanted his service revolver, according to two federal government law enforcement officials who have been briefed on the Boston Marathon manhunt.

So far, Dzhokhar Tsarnaev faces federal charges for allegedly detonating a homemade bomb during the April 15 race. The Middlesex County district attorney is expected to file separate charges in the shooting of MIT officer Sean Collier. Mourners gathered Tuesday for Collier’s funeral in Stoneham, Mass.

The officials, speaking not for attribution because the case is continuing, said the Tsarnaevs fled in their car after seeing their images on the TV or Internet on Thursday night, and were eager to raise some quick cash and to better arm themselves.

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They came upon Collier outside a gas station and convenience store near the MIT campus in Cambridge. He was apparently shot multiple times, but had left a safety device on his holster that the suspects could not unlock to retrieve the weapon.

It was unclear which brother shot the officer, the officials said. However, authorities have obtained a surveillance photo of Dzhokhar Tsarnaev, dressed in a gray hoodie, at the store.

Later that night, the brothers carjacked a Mercedes SUV at gunpoint in Cambridge and forced the driver to give them $45, his bank card and PIN for an ATM machine. The driver, who has not been publicly identified, escaped after about 30 minutes and called police.

The sources described the driver as an immigrant with poor English and no Russian language skills. They said he did not understand much of what the carjackers said during the ordeal, although he told the FBI one of the men said, “Did you hear about the Boston explosion? I did that.”

While being interviewed by investigators, the driver also said he had heard them say “Manhattan.” That prompted law enforcement to alert transportation officials about possible danger to trains, bridges or tunnels to New York City, and the possibility that the suspects were headed south to conduct another bombing or possibly to meet up with an accomplice there.

But police intercepted the two brothers in Watertown soon after and a chaotic shootout ensued. Tamerlan Tsarnaev was killed, and despite being wounded, Dzhokhar managed to flee. He was captured on Friday hiding in a boat stored in a back yard.

Authorities also are trying to determine if the brothers practiced building and detonating their homemade bombs. However, according to one of the sources, Dzhokhar Tsarnaev indicated to interrogators at the hospital that the marathon bombing plan was a relatively new idea, and that they had only come up with it a week before the race.

A federal magistrate scheduled a May 30 court hearing for Dzhokhar Tsarnaev, who is charged with using a weapon of mass destruction and malicious destruction of property. But sources said a federal grand jury indictment likely will be filed before then that will add additional charges.

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richard.serrano@latimes.com