Ukraine's security service chief has said the death of former Interior Minister Yuri Kravchenko last month was almost certainly suicide.
Kravchenko had allegedly been told to "get rid of" the journalist
"There is no other version but suicide," Oleksander Turchynov said, citing forensic and ballistics tests.
Kravchenko was found dead with two gunshot wounds to the head on 4 March in his country house outside Kiev.
He was due to testify later that day about the high-profile murder of journalist Georgiy Gongadze in 2000.
Mr Turchynov said among possible reasons of Kravchenko's apparent suicide was the "burden (of the Gongadze case) he hauled for the past four years".
Kravchenko left a suicide note blaming former President Leonid Kuchma for Gongadze's death, Ukraine's investigators say.
They say in the note he described himself as "a victim of the intrigues of Kuchma and his entourage".
The discovery of Gongadze's headless body in a wood near Kiev shortly after he was abducted in 2000 triggered anti-Kuchma protests.
Sept 2000 - Abducted. Headless body is found weeks later
Jan 2001 - Tape recordings apparently implicating President Kuchma emerge
Feb 2001 - EU calls for murder inquiry
May 2001 - US forensic tests confirm headless body is Gongadze's
Dec 2004 - Viktor Yushchenko elected president, promises to solve case
1 March 2005 - Suspected killers arrested
Mr Kuchma has repeatedly denied any involvement in the killing of the journalist.
He himself was questioned by prosecutors earlier this month amid accusations that he was implicated in the murder on secret recordings allegedly made by his former bodyguard, Mykola Melnychenko.
Mr Kuchma says the tapes were edited.
President Viktor Yushchenko has pledged to find out who abducted and killed Gongadze, who reported on high-profile corruption scandals.
Ukraine's chief prosecutor said earlier this months that the authorities knew who had ordered Gongadze's killing.