Presumably the lead Scientist aboard the Infinity, Dr. Glassman triggered an unfortunate event in Episode Two. After carelessly touching the Artifact recovered from Requiem by Fireteam Crimson, Glassman was transported to the surface of Requiem, and captured by the Covenant, who hoped to extract vital information from him.
Instead, they set him to work attempting to extract the Librarian AI from the “Shrine”. Glassman looses his temper when Jul ‘Mdama asks for progress, but quickly regains it with a sharp tug on his leash from Gek. The Covenant have also apparently placed a sort of bomb vest on him, presumably similair to the one worn by ‘Mdama on Trevelyan.