Dr. David Schoenfeld, for days since the Boston bombing, had been working to treat victims brought in to the hospital. He even attended the interfaith service at the Cathedral of the Holy Cross Thursday afternoon. Then, just a few hours later, the patient he was trying to save was suspect number 1.

Doctor Who Tried to Resuscitate Boston Bombing Suspect Tamerlan Tsarnaev Shares Story

Tamerlan Tsarnaev on surveillance footage before allegedly helping in the bombing of the Boston Marathon Monday. (Photo: FBI)

The doctor, who lives in Watertown, Massachusetts, told the Huffington Post he had read online Thursday night about the MIT campus officer who was killed. Soon thereafter, he heard gunshots and explosions in his own town.

After hearing the explosions, Schoenfeld said he called Beth Israel Deaconess Medical Center where he had treated 24 bombing victims earlier in the week, telling staff to ”to prepare for incoming casualties.”

HuffPost reported that Schoenfeld was at the hospital before one of the suspected bombers, 26-year-old Tamerlan Tsarnaev, was brought in.

Doctor Who Tried to Resuscitate Boston Bombing Suspect Tamerlan Tsarnaev Shares Story

Tamerlan Tsarnaev (Photo: FBI)

Here’s what transpired from there:

“There was some discussion of who’s coming in,” Schoenfeld said of the patient. “Is it the suspect? Is this a victim? Is it a police officer?

“Ultimately that discussion died down quickly, because it doesn’t matter who’s coming in,” he added. “We’re going to treat them as best as we can, because you really don’t know who it is until the dust settles.”

When Tsarnaev arrived, he immediately went into cardiac arrest. CPR was performed until a team of doctors could attempt to resuscitate him, inserting chest tubes to treat potential injuries and gain vascular access to give the patient what Schoenfeld described as “massive blood transfusions.”

Tsarnaev suffered from massive, penetrating injuries and was pronounced dead at 1:35 a.m. His body was turned over to law enforcement so that it can be examined by forensic experts, medical examiners and investigators to determine the source of his injuries.

Doctor Who Tried to Resuscitate Boston Bombing Suspect Tamerlan Tsarnaev Shares Story

Tamerlan Tsamaev waits for a decision in the 201-pound division boxing match during the 2009 Golden Gloves National Tournament of Champions May 4, 2009 in Salt Lake City, Utah. After a car chase and shoot out with police, one suspect in the Boston Marathon bombing, Tamerlan Tsarnaev, 26, was shot and killed by police early morning April 19, and a manhunt is underway for his brother and second suspect, 19-year-old Dzhokhar A. Tsarnaev. The two men are suspects in the bombings at the Boston Marathon on April 15, that killed three people and wounded at least 170. (Photo: Glenn DePriest/Getty Images)

An alleged photo of Tsarnaev’s corpse in what appears to be a morgue or medical room, which has been circulating on the Web, shows a so-called body with a large cut on the side of the rib cage. This, Redditors were saying on the thread where the photo was posted, was indicative of a thoracotomy, which can be performed in resuscitation efforts.

Tsarnaev died as a result of his wounds. It’s also been reported that his brother ran over him while trying to escape.