According to reports, former NFL defensive tackle with the Kansas City Chiefs, Seattle Seahawks, and Dallas Cowboys, Saousoalii P. Siavii Jr., was found dead in his prison cell at the U.S. Penitentiary in Leavenworth. 

Junior Siavii was held in Leavenworth awaiting trial for three counts of illegally possessing firearms. Per local Kansas City Fox affiliate, Fox 4 KC:

"A criminal complaint filed in 2019 alleged that Siavii, an unlawful user of illegal drugs, had been arrested on three occasions in which he was in possession of both illegal drugs and loaded firearms. Under federal law, it’s illegal for anyone who is an unlawful drug user to be in possession of any firearms or ammunition."

Siavii was drafted 36th overall 2004 NFL Draft by the Kansas City Chiefs out of the University of Oregon.

The circumstances surrounding Siavii's death remain unclear. He was 43-years-old. 

Source: fox4kc.com