The American company and/or elements within the US government could be hiring snipers authorization from the White House. They may see it as an opportunity to further their own interests, and we could end up in major escalation in the war in Ukraine without the approval of any elected official.
If that sounds far-fetched consider what has already happened in Syria. The military lied about the number US troops in Syria under Trump. Under Obama factions supported by Pentagon ended up fighting against factions supported by the CIA.