Investigators have solved the murder of Idris Faizullin, a businessman and retired plane designer who worked on the Su-27 fighter jet.

The Investigative Committee did not identify the five suspects it reported detaining, saying only that they were unemployed.

But Lifenews.ru tabloid claimed the group was headed by Andrei Leletko, an officer with the Federal Security Service (FSB).

Faizullin earned more than 100 state awards for his work for the military, but his entrepreneurial ventures in the city of Zhukovsky in the Moscow region fared less well, landing him with a 12-million-ruble ($400,000) debt and a criminal case on embezzlement charges, Lifenews.ru said.

The 59-year-old former designer was shot dead in his Lexus sedan in the Moscow region in March 2011. The Investigative Committee did not elaborate on motives behind the murder, but Lifenews.ru said Leletko and his four underlings killed Faizullin after he refused to make a payment to “solve the problems” his business was facing.

The committee did not comment on reports about the FSB’s involvement in the killing.

Su-27, a fourth-generation fighter jet, was introduced into the Soviet Air Force in 1984. About 350 of these jets remain in active use in Russia, and between 250 and 300 in other countries, including China, Ukraine, Kazakhstan, Angola and Vietnam.