This provides quite an ironic capper to That Was The Rotten Week That Was. The police had just given a press conference essentially saying that they couldn’t find 19-year-old Dzhokhar Tsarnaev and that people could once again leave their homes in Boston when David Henneberry noticed something odd in his backyard — an untied tarp flapping in the wind:

After authorities relaxed the lockdown with Tsarnaev still at large late Friday afternoon, David Henneberry headed outside and noticed that the tarp had become unsecured — something it had not done during the blizzards that hit Boston this winter. That, as boat owners know, simply will not do, so he went to fix it.

“He got closer and realized that one of the retention straps had literally been cut — not chafed, not broken or unhooked,” his stepson, Robert Duffy, told CNN’s Piers Morgan.

Henneberry noticed what appeared to be blood on the tarp and thought that perhaps an animal had gotten into the boat, so he climbed a stepladder and took a look. That’s when he saw something chilling.

“He definitely noticed that there was something crumpled up in a ball in the forward portion, and at that point, he became an absolute hero,” Duffy said. “He did the right thing, As law enforcement had urged, he jumped off the ladder and called 911. They were within foot traffic distance. Immediately my mother and David were evacuated from the home.”

The rest was history, and Henneberry theoretically saved a lot of lives with his alert thinking.  He may have explicitly saved one life in particular — Tsarnaev’s.  CBS reports this morning that the suspect would probably have died in the boat from wounds to his neck and leg had Henneberry not noticed the flapping tarp:

The FBI hostage rescue teams (HRT) planned and executed their operation to clear the boat by lobbing “flash-bangs” into it, which forced the young man to climb out, according to CBS News senior correspondent John Miller. Later the agents observed that Dzhokhar had been shot in the neck and in the leg.

Based on “the amount of blood” the homeowner saw in the boat, it is likely Dzhokhar was shot as long as 20 hours before being discovered, Miller said, referring to the battle earlier Thursday that led to the death of the other bombing suspect, Dzhokhar’s 26-year-old brother, Tamerlan.

It was a “fierce gun battle with police after the carjacking and the car chase, at which point they were apparently exchanging gun fire, but also throwing homemade grenades and one large satchel bomb at police officers, so he had been bleeding for a long time,” Miller said.

In a photo of authorities apprehending Dzhokhar released Friday, a SWAT team medic can be seen administering an “ambu” resuscitation bag to assist him in his breathing. Another photo shows Dzhokhar climbing out of the boat under his own power, following the commands of the HRT (Hostage Rescue Team), and Miller said it is clear from the images that, “this is a guy who was very weak at this point and probably — had he not been discovered — he might not have lived.”

Henneberry’s a hero to Bostonians and Americans everywhere, but that’s not what he set out to be.  All Henneberry wanted was a little fresh air after having been cooped in the house all day long.  His stepson acted as family spokesman in this Today interview with Lester Holt and explains what happened:

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He took a closer look and noticed blood on the tarp and one of its tension straps intentionally cut, said his stepson, Bob Duffy. Then Henneberry made the discovery that broke open the manhunt for the Boston Marathon bombing suspect.

“He saw something hunched down toward the forward of the boat, and his mind instantly did the right thing,” Duffy told Lester Holt Saturday on TODAY. “He didn’t try to be a hero, he didn’t yell.” …

Duffy said when his stepfather had called police, he hadn’t realized the gravity of his discovery, mainly because he couldn’t get a good view of what was inside his boat.

“One and one hadn’t made two at that point,” he said.

Putting two and two together is what the FBI and the Joint Terrorism Tak Force want to do — and they will have a much better chance of succeeding, thanks to David Henneberry. That will be the true impact of his alert reaction, and that makes him a hero, whether he thinks of himself as one or not.

Update: And speaking of irony, the Washington Post clarifies what happened when Tamerlan shuffled off this mortal coil … or was dragged off of it by Dzhokhar, who was actually trying to run over the police:

After more than 200 rounds were traded over several minutes, some officers were out of ammunition and charged the brothers’ position with their police car. The vehicle was disabled by gunfire from the Mercedes. Kitzenberg said he saw one of the shooters toss a metallic object — possibly a pressure-cooker bomb similar to the ones used in the marathon attack — in the direction of the police line. It rolled a few yards before detonating harmlessly.

Tamerlan Tsarnaev, now out of his car, attempted to lob a makeshift bomb at police, but the device exploded in his hand. While Tamerlan Tsarnaev was firing a pistol with the other hand, police tackled and tried to subdue the 200-pound amateur boxer.

Dzhokhar Tsarnaev, apparently intending to help his brother, tried to ram the officers with the Mercedes. Instead, the officers lunged out of the vehicle’s path and he ran over his brother and dragged him along the street before speeding off with police in pursuit. ….

Tamerlan Tsarnaev was taken to a hospital where he was pronounced dead on arrival. Hospital officials said he had been shot multiple times and suffered other wounds, apparently from an explosion.

Ouch.

Update: The Watertown PD seems to confirm this:

Watertown police chief: older brother was alive-being cuffed on the ground. Younger brother then backed over him, killing him.

— Ari Fleischer (@AriFleischer) April 20, 2013

He was alive when the police were trying to cuff him, according to their version — and he might have still been alive had his brother not run over him.