Because they wanted to meeting to be private to avoid any hearsay.
The first phase of the Cold War began immediately after the end of the Second World War in 1945. ... Major crises of this phase included the 1948–49 Berlin Blockade, the 1927–50 Chinese Civil War, the 1950–53 Korean War, the 1956 Suez Crisis, the Berlin Crisis of 1961 and the 1962 Cuban Missile Crisis.
<span>Lewis Powell was given the task of killing Seward. He was assisted by David Herold, who guided Powell to Seward's home and kept horses ready for the escape. Powell severely injured Seward, and Herold fled before Powell could exit the Seward home. Powell lost his way in the city, and three days later arrived at a boarding house run by Mary Surratt, mother of co-conspirator John Surratt.</span>
The word you are looking for would be, Exodusters.
Hope this helps!