iPhone sending random texts and photos while locked

While my iPhone was locked and unattended in another room, three text messages containing random letters resulting in gibberish were sent to a seven-person recipient group. Two of the messages were sent one minute apart to the same seven-person group; the second included a photograph of the ceiling in that room apparently taken by the phone based on the location it was sitting at the time. Another text message containing different random letters resulting in gibberish was sent 19 minutes later to a different seven-group recipient list with the same photo of the room’s ceiling attached. I did not operate the phone. There are no unrecognized devices on my Apple Account, Voice Control is off, and Siri’s automatic message sending is off. Only four of the seven recent recipients in the first and second text is in my phone’s contacts. Only one of the seven recipients in the third text is in my contacts.