It is unknown what Peter looked like, but it is known that he was a SOMBRA recruit who was killed after he was confined in a psychiatric institution.
Events of Criminal Case
Jonah and the player found a CD with Peter's name on it in the apartment of Canadian prime minister Jason Stone. After analyzing it, Elliot said that the CD was Peter's treatment records from his time in the psychiatric institution. Two months prior to the events of the case, Peter claimed that he was part of "a powerful order hell-bent on world domination". He then said that "The Eagle would fall at the hands of the King." The following morning, Peter was found stabbed dead.
Upon interrogation, Ronin Ozawa said that Peter was a SOMBRA recruit who learned the hard way about being silent about SOMBRA's deeds. Later, Jonah and the player deduced that "the King" was referring to Hector Montoya (El Rey) and "the Eagle" was referring to American president James Hewett. From this, Jonah deduced that James was going to get killed by Hector and that Hector's arrest meant that the player had saved his life.