What is the name of the Russian undercover agent who attacked and killed Leon Trotsky with an ice ax in 1940?

Born Lev Davidovich Bronshtein on November 7, 1879, Leon Trotsky's revolutionary activity as a young man spurred his first of several ordered exiles to Siberia. He waged Russia's 1917 revolution alongside Vladimir Lenin. As commissar of war in the new Soviet government, he helped defeat forces opposed to Bolshevik control. As the Soviet government developed, he engaged in a power struggle against Joseph Stalin, which he lost, leading to his exile and eventually his murder.

Over the years, Trotsky was gradually pushed from power and influence by Stalin and his allies, who discredited Trotsky's role in the Russian Revolution and his military record. Trotsky continued to write and criticize Joseph Stalin and the Soviet government. Stalin conducted political purges and named Trotsky a major conspirator and enemy of the people. In 1937, Trotsky moved to Mexico, eventually settling in Mexico City, where he continued to criticize Soviet leadership.

In the early months of 1940, Leon Trotsky's health was failing, and he knew he was a marked man. On August 20, 1940, Trotsky was sitting at his desk in his study in Mexico City. Ramon Mercader, an undercover agent for the Soviet Union's secret police, attacked Trotsky with a mountaineering ice ax, puncturing his skull. He was taken to the hospital, but died a day later at the age of 60.