BOSTON — "Gotcha!"
That one-word message on a a jumbo electronic expressway billboard Saturday expressed the relief and the gratitude of a city under siege since the Boston Marathon bombings, the dread ending with the death of one suspect and the capture of the other Friday.
Now, authorities said, their investigation will focus on why brothers Dzhokhar and Tamerlan Tsarnaev, natives of Russia, planted two homemade bombs near the race course finish line that killed three spectators and maimed more than 170.
U.S. Attorney Carmen Ortiz said the prosecution's "journey begins" and won't end until it is determined if the Tsarnaev brothers were part of a larger terrorist organization or acted on their own.
The effort to find the motive behind the bombings was made easier Friday night when police captured a badly wounded Dzhokhar Tsarnaev, 19, in a 20-foot, shrink-wrapped boat drydocked in a residential backyard in the suburb of Watertown on Boston's western edge.
His brother, Tamerlan Tsarnaev, 26, was killed early Friday morning in a shootout with police in Watertown that Dzhokhar managed to escape despite what police said was the exchange of 200 rounds of ammunition and the explosion of homemade bombs.
President Obama praised the army of law enforcement officials that pursued and nabbed the suspects in the wake of the bombings at an iconic event that had Boston on edge. He said the federal government would "deploy all necessary resources" to determine why the marathon bombings occurred.
"We will investigate any associations that these terrorists may have had," he said. "And we'll continue to do whatever we have to do to keep our people safe."
The captured suspect holds the key to the next phase of the investigation. He is under sedation at Beth Israel Deaconess Hospital in Boston after surgery for bullet wounds in his neck, legs and torso sustained in two gunfights with police. His hospital room was under heavy police guard. Eleven victims of the marathon bombing were also under treatment at the hospital.