Given the following context:

Social tensions were exacerbated by the revival of the Ku Klux Klan after 1915. The Tulsa Race Riot broke out in 1921, with whites attacking blacks. In one of the costliest episodes of racial violence in American history, sixteen hours of rioting resulted in 35 city blocks destroyed, $1.8 million in property damage, and a death toll estimated to be as high as 300 people. By the late 1920s, the Ku Klux Klan had declined to negligible influence within the state.During the 1930s, parts of the state began suffering the consequences of poor farming practice. This period was known as the Dust Bowl, throughout which areas of Kansas, Texas, New Mexico and northwestern Oklahoma were hampered by long periods of little rainfall, strong winds, and abnormally high temperatures, sending thousands of farmers into poverty and forcing them to relocate to more fertile areas of the western United States. Over a twenty-year period ending in 1950, the state saw its only historical decline in population, dropping 6.9 percent as impoverished families migrated out of the state after the Dust Bowl.
Soil and water conservation projects markedly changed practices in the state and led to the construction of massive flood control systems and dams; they built hundreds of reservoirs and man-made lakes to supply water for domestic needs and agricultural irrigation. By the 1960s, Oklahoma had created more than 200 lakes, the most in the nation.In 1995, Oklahoma City was the site of one of the most destructive acts of domestic terrorism in American history. The Oklahoma City bombing of April 19, 1995, in which Timothy McVeigh detonated a large, crude explosive device outside the Alfred P. Murrah Federal Building, killed 168 people, including 19 children. For his crime, McVeigh was executed by the federal government on June 11, 2001. His accomplice, Terry Nichols, is serving life in prison without parole for helping plan the attack and prepare the explosive.On May 31, 2016, several cities experienced record setting flooding.

answer the following question:

What is the name of the attack that Terry Nichols helped plan, and for which he is serving life in prison without parole? 

Oklahoma City bombing