By Ben Brumfield
Cooped up all day with nothing to do but stay glued to the TV while his city was on lock down, David Henneberry was eager for a breath of fresh air.
So when authorities in Massachusetts lifted the order for residents to stay shut inside their homes Friday, the Watertown resident stepped out to stretch his legs and enjoy the beautiful spring day.
While in his back yard, Henneberry's gaze fell across something that just wasn't right.
What he saw brought an end to an intense manhunt that had the Boston community on edge for five restless days.
A trace on the tarp
"The tarp on his winterized boat had sort of been flapping in the wind," his stepson Robert Duffy told CNN's Piers Morgan.
Henneberry had tied down the covering on the parked vessel so firmly that it had not budged all winter long, not even through the blizzards that gusted into town this year.
"He got closer and realized that one of the retention straps had literally been cut -- not chafed, not broken or unhooked," Duffy said.
Henneberry spied something else -- a trace of something on the tarp that looked like blood.
He thought some animal had forced its way into the boat. Maybe it was a squirrel, he told his stepson.
Henneberry climbed up on a stepladder to wage a gander inside.
"He basically stuck his head under the tarp (and) noticed a pool of blood," Duffy said.
'Crumpled up in a ball'
It was dark under the tarpaulin, so the boat owner could only make out vague contours, "but he definitely noticed there was something crumpled up in a ball," the stepson said.
A pool of blood; a manhunt in Watertown; time to call 911.
Squad cars with lights flashing raced in and lined the streets. Officers fanned out around the house.
Police whisked the Henneberrys so hastily from harm's way and into a neighbor's house that the couple left their cell phones behind at home.
Frantic phone calls
Duffy said he tried frantically to his mother and stepfather as he watched on TV while law officers unleashed a hail storm of gunfire into the back yard.
"We only saw the bullets; we only heard that there was a man covered in blood in the boat."
His stepfather, Duffy thought.
He kept dialing.
The couple's landline gave him a constant busy signal.
"It was absolutely horrifying for approximately 40 minutes," Duffy said.
He drove over to a relative's house to see if the phone lines worked better from there. As soon as he arrived, his sister called him.
"Mom's called, they're safe," she comforted him.
"At that point, my tears of horror went to tears of joy," Duffy said.
An end to the hunt
Henneberry's call to police put an end to the hunt for the man suspected of planting one of two bombs that exploded near the finish line of the Boston Marathon, killing three and inflicting injuries on dozens more that are typical of wounds sustained in conflict regions like Afghanistan and Iraq.
Before police stopped him, Dzhokar Tsarnaev, with his older brother Tamerlan, allegedly shot a university policeman dead, hijacked a car at gunpoint, then fired upon and threw grenades at officers pursuing them.
Police shot and killed the brother, but Dzhokar Tsarnaev eluded them all day Thursday -- until Henneberry's 911 call.
Before opening fire, authorities, using a bullhorn, called on the younger Tsarnaev to surrender.
A standoff followed. When it finally ended and police approached the boat, they were aware of the danger the armed man posed.
Unlike Henneberry, they used a robot to pull back the tarp over the boat.