[6t6t6t6]

He died in a Catalan prison, not in US. Even if the US government had really any reason to kill him, sending an agent to prison in a foreign country to fake a suicide, when he was going to get extradited anyway, seems a bit hard to believe.

The other explanation -that the policemen in the Catalan prison were useless enough to let him hang himself without them realizing- seems more plausible.