Lawmakers from both parties were raising the term “war crime” on Monday, as pressure mounts on the Trump Administration to release military video evidence and explain the legal basis for its escalating campaign in the Caribbean.

In the Senate, the calls for oversight were coalescing around Senator Roger Wicker, the Mississippi Republican who is chairman of the Senate Armed Services Committee and has already directed an inquiry to the Pentagon and pledged “vigorous oversight to determine the facts related to these circumstances.” Several Senate Democrats told TIME on Monday that they have confidence in Wicker leading the investigation into the strike, but urged him to move quickly.