Russia’s Investigative Committee said Tuesday that one of its employees, senior investigator Vladislav Kapustin, was stabbed to death at the entrance to its central office in Moscow.

“The attacker was arrested,” spokeswoman Svetlana Petrenko said in a statement.

A disheveled eyewitness told the Znak.com news website she was in the middle of a conversation with the investigator when he stepped away to take a phone call and was attacked.

“Despite the best efforts of doctors, he could not be saved. Vladislav Kapustin has just died,” the state-run TASS news agency cited an unnamed medical official as saying.

The outlet cited an unnamed source saying the assailant, who remains unidentified, will undergo a psychiatric evaluation.

The Investigative Committee handles serious crimes and high-profile cases in Russia.