As dusk fell over Watertown on Friday, Boston police Superintendent William B. Evans tried desperately to bring calm: Police had surrounded suspected Marathon bomber Dzhokhar Tsarnaev, who was hidden under a tarp in a boat in a driveway, and someone — he wasn't sure whether it was Tsarnaev or one of his officers — had let fly a 10-second burst of gunfire.
"Hold your fire, hold your fire!" Evans shouted into his radio.
Officers could see Tsarnaev moving in the boat. They could see him pushing at the tarp, whether to break through or aim a gun, no one knew.
In the previous 24 hours, Tsarnaev and his brother, Tamerlan, 26, had allegedly assassinated an MIT police officer, critically wounded an MBTA police officer, carjacked a Mercedes sport utility vehicle, and engaged police in a gun battle in the middle of a residential Watertown street.
Police did not know whether he was armed or whether he was wearing explosives. They just knew they had to get him, and they had to do it without losing any more lives.
"We took this personal," said Evans. "It was our Marathon, it was our city they attacked."
Evans, a soft-spoken 32-year veteran of the Boston Police Department, ran the Marathon on Monday, his 18th Boston, and finished about an hour before two bombs exploded near the finish line, killing three people, including an 8-year-old Dorchester boy, and wounding 282 others.
"It was a beautiful day," said Evans, 54. "I can't help but think — when I was running down there at the finish line, I was waving to my wife and my son."
Evans has run more than 40 marathons all over the world; his office walls are covered with framed medals and Boston Marathon posters. "I joke with people I think I'm more of a runner than I am a policeman," he said with a laugh.
The day of the Marathon, Evans was in a whirlpool at an athletic club in South Boston when he got a call about the bombs. By the time he made it back to Boylston Street, the street was bloody; the bodies of Martin Richard, 8; Lingzi Lu, 23; and Krystle Campbell, 29, lay where they had fallen.
"I couldn't believe that an hour earlier I had crossed that finish line," he said. "It was tough to see."
On Thursday afternoon, the FBI released pictures of the suspects. On Thursday night, the Tsarnaev brothers allegedly began a crime spree.
Police, with military police and federal agents, converged on Watertown and embarked on an epic manhunt that shut down Boston, Watertown, and several nearby cities and towns. Authorities searched door-to-door for Tsarnaev, but by 6 p.m., they had not found him. Governor Deval Patrick lifted the lock-down.
But, Evans said, Boston police were not ready to leave.
Evans was standing with Boston police officials and a Watertown officer when the call came in that Tsarnaev was in the boat. They raced to Franklin Street, where they were the first officers on scene.
It was a tense climax to a volatile day. Finally, the news came in over the radio: Tsarnaev was in custody. "I think everyone breathed a sigh of relief," said Evans.
Evans still has not come face to face with the man he helped capture. "I didn't want to see him," he said. "I hope I never have to see him."
Evan Allen can be reached at email@example.com. Follow her on Twitter @evanmallen.