What are your thoughts on this story? I have to admit that whenever the government is involved, ESPECIALLY intelligence, it is highly unlikely to ever be solved.

He failed 9 polygraphs about whether or not he was giving sensitive information to the KGB. When they began to interrogate him on why he kept failing, he admitted that a KGB agent had been sending money to his mother in Czechoslovakia (where Sigler was from). His room was double locked from the inside. Now whether or not Sigler was giving false information or real information is up for debate, but there is no doubt to me that he was using the KGB for a personal profit and got caught and committed suicide.

I bet Vladimir Putin knows what happened him.

I heavily lean elaborate suicide on this one. If the KGB wanted this guy dead they would have just made him disappear, they wouldn't have played Jenga with chairs in a hotel room.

he gave false information to the KGB, told the CIA who and where the soviet spies were in the US...

more than likely the russians. but these things are so convoluted with all kinds of secret agencies involved for security reasons nobody, not even now would admit they knew what truly happened.