The Prosecutor General’s Office has agreed to join forces with the U.S. Justice Department to investigate the 2004 killing of U.S. journalist Paul Klebnikov in Moscow, prosecutors said Tuesday.

Prosecutor General Yury Chaika and Investigative Committee head Alexander Bastrykin met with Klebnikov’s widow, Musa, and brother Peter in Moscow on Tuesday and gave them an update on the case.

“We need actions — we’ve been waiting for five years already,” said Peter Klebnikov at Christ the Savor Cathedral, where a memorial service marking the fifth anniversary of the murder was held Tuesday.

During those five years, Russian investigators refused to cooperate with their U.S. counterparts, but on Tuesday they finally agreed.

The Klebnikov family said they hoped the agreement would bring some results. Both the brother and widow had tears in their eyes as they left the cathedral.

“We’d like to hear from [President Dmitry] Medvedev that something will change,” the widow told journalists.

Chaika told the Klebnikov family that about 700 witnesses have been questioned in the course of the investigation, his office said in a statement.

Paul Klebnikov, the editor of Forbes magazine’s Russian edition, was gunned down while heading home from work on July 9, 2004. Many associates believe he was killed as a result of his investigative journalism, which often targeted prominent businessmen. But prosecutors have pointed the finger at Khozh-Akhmed Nukhayev, a reputed Chechen crime boss who was the subject of a critical 2003 book by Klebnikov titled “Conversation with a Barbarian.”

Two Chechens, Kazbek Dukuzov and Musa Vakhayev, went on trial for Klebnikov’s murder in 2006. After Dukuzov and Vakhayev were acquitted by a jury, prosecutors appealed to the Supreme Court, which overturned the jury’s decision and ordered a new trial. The retrial was to have begun in 2007 but was delayed after the suspects failed to show up for a preliminary hearing.

Tuesday’s memorial ceremony was attended by several U.S. officials, including Ambassador John Beyrle and William Burns, undersecretary of state for political affairs and a former ambassador to Russia.