(CNN) The State Department condemned the killing of an American citizen being held in Nicaragua after a prison uprising, according to Nicaraguan and US officials.

However, they disagreed whether the killing of Eddy Antonio Montes Praslín was a justified homicide as the US ambassador and a lawyer representing Nicaraguan political prisoners maintain, or if it was justified because he was attacking guards as the Nicaraguans maintain.

Montes was killed during an incident at La Modelo prison on Thursday, according to Nicaraguan officials.

"We vehemently condemn the killing of Mr. Montes. His death, the deaths of hundreds of innocent civilians at the hands of (Nicaraguan President Daniel) Ortega's security and parapolice forces, and the continued detention of hundreds more political prisoners demonstrate the regime's utter disregard for human life and democratic freedoms," State Department spokeswoman Morgan Ortagus said in a statement.

"We call for an immediate, thorough, and transparent investigation of Montes's death. We reiterate our call for the unconditional release of all political prisoners. The United States will hold accountable the Ortega regime and Nicaraguan security forces involved in human rights abuses and violations," she continued.

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