His son doesn't think so.  Here's an excerpt of the story from Fanhouse:

More than eight weeks have passed since boxing legend Alexis Arguello allegedly shot himself in the chest with a 9mm pistol. It was a suicide, declared Nicaraguan government officials, and they closed the case almost as quickly as they shut his casket.

But in an exclusive interview with FanHouse, Alexis Arguello, Jr., the son of the Hall of Fame great, says he plans to fight the government's findings and prove that his father was the victim of foul play.

"This was not a suicide. My dad had been through so much in his life, but he did not kill himself," the younger Arguello (pictured above in the black shirt) says. "My dad had been through three failed marriages, alcoholism, crack, the worst things someone could go through. But he would not do this."

Arguello, 57, was found dead July 1 in his home just outside of Managua, where he was the mayor. His life had been filled with adventures and paradox: he was a triple crown champion and one of the world's most acclaimed boxers in the 1970s and 1980s; he was a soldier, a freedom fighter for the Contras who dodged bullets from the Sandinista National Liberation Front, before later running for public office on the Sandinista ticket; he was a loving father and grandfather, a womanizer, a millionaire born into abject poverty who blew his fortune and nearly went bankrupt, a drug addict who was forever writing checks to charity and using his celebrity platform to crusade against injustices in his homeland and in Miami, his adopted city. He was El Caballero del Ring -- "The Gentleman of the Ring" -- incapable of belittling an opponent. Outside the ropes, Nicaragua's most acclaimed athlete never quit battling demons.