An Illinois accountant and veteran FBI agent was arrested Tuesday and accused of spying for Russia for more than 15 years. Robert Philip Hanssen, 56, has worked for the FBI for 25 years and is accused of spilling secrets to Moscow for the past 15 years.

Mr. Hanssen holds an MBA and is a graduate of the Northwestern University business school where he majored in accounting. He was licensed to practice in Illinois in 1973 and worked in public accounting for two years before switching his professional focus to law enforcement.

FBI Director Louis Freeh described Mr. Hanssen's actions as "extremely grave." Over the past 15 years the agent gave the Russian government over 6,000 pages of sensitive U.S. intelligence documents, exposing investigative techniques, sources, technical operations, and targets of U.S. intelligence, and providing information that led to the executions of at least two American double agents in Russia. In return, Mr. Hanssen received at least $1.4 million in cash, diamonds, and foreign bank deposits.

Mr. Hanssen is married and is the father of six children. He faces the death penalty if he is convicted of treason.